information about scsi

8/13/2019 Information about scsi

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ML-530

Form Factor:

Processor: Pentium III Xeon 866 MHz

Processors Qty.: 1

Installed Memory: 128 MB (SDRAM)

Platform: PC

Processor

Processor Manufacturer: Intel

Processor Type: Pentium III Xeon

Processor Speed: 866 MHz

Installed Qty: 1

Max Supported Qty: 2

Processor p!rada"#l#ty: Upgr!"le

Memory

Installed $%M: 128 MB

$%M Tec&nolo!y: SDRAM

Max#mum $%M: # $B

'ard (r#)e*nd Stora!e +ontroller: ID% & %ID%

,etor#n!

,etor#n! Type: 'etor A!pter

(ata L#n Protocol: %t*ernet + ,-t %t*ernet

Mot&er"oard

Installed L* +ac&e Memory: 2.6 /B

/#deo utput Interface: PCI

+( 1 (/(+( 1 (/( Type: CD0RM

t&er (r#)es

Floppy Type: 3.4 13## MB 5lopp

%ud#o 1 /#deo

Max. /#deo $esolut#on: 1677 1277
http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3023.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3264.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_5943.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_1724.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14410.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3305.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14401.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14393.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3023.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3264.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_5943.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_1724.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14410.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_3305.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14401.epi.html');http://whatis%28%27http//img.shopping.com/cctool/WhatsIs/1/96263_14393.epi.html');


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Installed /#deo Memory: # MB

(#mens#ons

: 9er-

M#scellaneous

2xter#or +olor: :*ite

Product I(: 27121868

More Informat#on

(eta#ls: Comp; Proerll 20--tem per5ormn?e3In !!ition to it- le!ing per5ormn?e@ t*eM


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NOTE: Ma+,mum memory ac&,e%ed us,n 204* M$ IMMs

Netor! "o#tro$$er /mbedded 5-3!3 6ast /t&ernet 5I- P-I !07!00 8,t& 9OOn :5)

Stor%&e "o#tro$$er Interated ual -&annel 9,de o8er

ML530T02 X2./0-512KB, 1024MB, 2P306489-xx1

Processor >8o Intel Xeon 2.*0 GHz Processor standard

Processor System Bus 400 MHz system bus

Processor Memory !2"#$ le%el 2 cac&e per processor

Memory !024 M$ ('tandard) !3*4 M$ (Ma+,mum) P-!00 d%a'1M 2! ,nterlea%ed memoryNOTE: Ma+,mum memory ac&,e%ed us,n 204* M$ IMMs


Stor%&e "o#tro$$er Interated ual -&annel 9,de


4/27

180285-xx1

Processor Memory !2"#$ le%el 2 cac&e per processor

Memory !024 M$ ('tandard) !3*4 M$ (Ma+,mum) P-!00 d%a'1M 2! ,nterlea%ed memoryNOTE: Ma+,mum memory ac&,e%ed us,n 204* M$ IMMs


Stor%&e "o#tro$$er Interated ual -&annel 9,de o8er

Recommended UseCorporate business

Product Form FactorRack-mountable

Built-in DevicesStatus LCD

Server Scalability4-way

Front Accessible Bays Qty4 Hot-Swap Bays Qty12

Processor

TypeIntel Pentium III Xeon 9 !"#

nstalled Qty2


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!a" Supported Qty4

Up#radability$p%ra&able

!ainboard

$%ipset typeSer'er(orks Ser'erSet III ") Data bus speed1 !"#

$ac%e !emory

TypeL2 cac*e - +&'ance& ,ranser Cac*e

nstalled Si&e4 !. /installe&0 !. /ma30

RA!

nstalled Si&e1 . 15 . /ma30

Tec%nolo#ySDR+! - )CC

!emory Speed1 !"#

Form FactorDI!! 15-pin

FeaturesRe%istere&

Up#rade Rule4 mo&ules at a time

Stora#e $ontroller

Type1 3 SCSI - Inte%rate& - PCI

$ontroller nter'ace Type$ltra2 (i&e SCSI $%annel Qty2

RAD (evel6one

Stora#e $ontroller )*nd+

Type1 3 ID) - Inte%rate& - PCI

RAD (evel6one

Stora#e

Floppy Drive78: 1844 !. loppy

Hard Drivenone8

Hard Drive )*nd+6one

,ptical Stora#e


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TypeCD-R;! - ID)

rite Speed6+

Rewrite Speed6+

!edia (oad Type,ray

.rap%ics $ontroller

TypePCI - Inte%rate&

.rap%ics Processor / 0endor+,I R+) IIC

0ideo !emory4 !.

Supported Display .rap%ics


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!in operatin# temperature B?

!a" operatin# temperature9 B?

,peratin# %umidity ran#e2 - E

Sound emission &.+

,peratin# System / So'tware

,S ProvidedCD-R;!

,S $erti'ied!icrosot (in&ows 2=

6o'ell 6et(are=!icrosot (in&ows 6,=

SunSot Solaris=

Linu3=

I.! ;S2 (arp=SC; ;penSer'er=

.anyan or o5 t*e mu?* 5-ter PCI %pre-- inter5?e3 *i- men- ou re looing t 5or?e!trn-ition in t*e grp*i? -e?tor@ t*u- ou rell !on=t *>e lot o5 ?*oi?e in t*e ?oming er-3 Att*i- point (Augu-t@ 2778) ?*oi?e- in A$P ?r!- repre-ent le-- t*n .E o5 >il"le ?r!-@ n! t*elte-t ?*ip-et- ?n not "e 5oun! in t*e 5orm 5?tor3

:*ile e=>e -pent plent o5 time n! energ impro>ing t*e -pee! o5 pro?e--or-@ memor@ n!ot*er prt- o5 t*e PC e=>e !one >irtull not*ing it* t*e min ?onne?tion "eteern mn!e>i?e-0PCI3 A- -u?* e re -tu? it* te?*nolog in our PC- n! Ser>er- t*t -till run- t t*e-pee!- n! "n!i!t* e ere ?om5ort"le it* in t*e 7=-3 PCI - e no it i- *ol!ing u- "?0 it i- "ottle ne? 0 limittion to t*e mimum per5ormn?e o5 our --tem-3


8/27

:e ll nt t*e mo-t 5rom our PC3 o get t*e mo-t out o5 our PC e mu-t remo>e ll "ottlene?-(o"-t?le- to per5ormn?e)3 o t*t en! e mu-t turn to t*e net "e-t lternti>e PCI %pre--3

2as#n! #nto It - %ll a"out t&e &y4

I5 ou *>e re! m gui!e to t*e ,ront Si!e Bu-t*en ou re 5milir it* t*e nlog o5 PC -

"eing lie ?it it* mn ro! ("u-e-) in it t*t mo>e ?r- (!t) to n num"er o5 !e-tintion-3i-it m eplntion o5 PCI 5rom t*t rti?le

PCI Bus- The PCI bus connects your expansion cards and drives to your processor and othersub systems. On most systems the bus speed of the PCI bus is 33MHz. If you o hiher thanthat! then cards! drives! and other devices can have prob"ems. The exception to this is found inservers. In some servers you have a specia" #$-bit %extra &ide' ##MHz PCI s"ots that can acceptspecia" hih-speed cards. Thin( of this as a doub"e sized passin "ane on a ma)or road thata""o&s hiher speed cars to o throuh.

'o in m pre>iou- rti?le I mentione! -pe?il tpe o5 PCI (6# "it)3 *e re-on 6# "it *elp- i-t*t it impro>e- t*e "and#dt&o5 t*e PCI Bu-3 Bn!i!t*@ normll epre--e! in MB per-e?on!@ i- "-i?ll me-ure o5 t*e mount o5 !t t*t ?n "e pu-*e! t*roug* -omet*ing t

one time3

I5 ou e>er *>e -t in our ?r looing t t*e "? "umper o5 not*er ?r !uring ru-* *our t*enou pro""l *>e goo! i!e o5 *t=- going on in t*e mo!ern PCI Bu-3 9ou=>e got too mn?r- (!t) going t*roug* too nrro n! too -lo ro! (p?i "u-) t one time3

and#dt&

PCI %pre-- in ll it=- 5l>or- 1@ 2@ #@ 8@ 16 n! 2 ll *>e mu?* greter "n!i!t* t*n"-i? PCI3

+ommon uses and t&e#r Max and#dt&

PCI 12 MB&-A$P 8X 2@177 MB&-

PCI %pre-- 1 2.7 F.77G MB&-

PCI %pre-- 2 .77 F1777G MB&-

PCI %pre-- # 1777 F2777G MB&-

PCI %pre-- 8 2777 F#777G MB&-

PCI %pre-- 16 #777 F8777G MB&-

PCI %pre-- 2 8777 F16777G MB&-

USB 237 (M Po--i"le) 67 MB&-

ID% (AA177) 177 MB&-

ID% (AA1) 1 MB&-SAA 1.7 MB&-

SAA II 77 MB&-

$ig"it %t*ernet 12. MB&-

I%%%1#B F,ireire 877G 177 MB&-
http://www.directron.com/fsbguide.htmlhttp://www.directron.com/fsbguide.html


9/27

* +ote , - ince PCI xpress is a seria" based techno"oy! data can be sent over the bus in t&o directions at once. +orma" PCI isPara""e"! and as such a"" data oes in one direction around the "oop. ach ,x "ane in PCI xpress can transmit in both directions atonce. In the tab"e the first number is the band&idth in one direction and the second number is the combined band&idth in bothdirections. /"so p"ease note that in PCI xpress band&idth is not shared the same &ay as in PCI! so there is "ess conestion onthe bus.

pdate "le "o>e ?ontin- -pee!- 5or PCI %pre-- 137 "u-3 ,or >er-ion 237@ multipl ll"n!i!t*- " 23 ,or emple PCI %pre-- 237 16 -lot *- m "n!i!t* o5 8777 MB&-

one or 16777 MB&- "ot* -3

* +ote 0 - 1i re&ire 2 has a band&idth of 42#.$30 Mbit5s this converts over to bet&een 62 and 66 M75s.

In?re-e! "n!i!t* ?n "e e;ute! into in?re-e! --tem per5ormn?e3 :e=>e long non t*t to get t*e mo-t out o5 ourpro?e--or ou nee! to get - mu?* in5ormtion into it - po--i"le@ - ;ui?l - po--i"le3 C*ip-et !e-igner- *>e ?on-i-tentl!!re--e! t*i- " in?re-ing ,ront Si!e Bu- -pee!-3 *e pro"lem it* t*i- i- t*t 5ront -i!e "u- -pee! in?re-e- t*e -pee! o5trn-5er "eteen t*e memor n! CPU "ut o5ten ou=>e got !t t*t=- ?oming 5rom ot*er -our?e- t*t nee!- to get to t*ememor or CPU lie !ri>e-@ netor tr55i?@ >i!eo@ et?3 PCI %pre-- !!re--e- t*i- pro"lem *e! on " ming it mu?* 5orm- t*enou *>e grp*i?- ?*ip-et t*t -

Basic Differences

PCI-X uses a parallel interconnect along a bus that is shared with other PCI-X devices, justlike PCI. In fact, PCI-X is best thought of as "PCI-eXtended", as it is simpl an e!tension ofthe legac PCI #-bit format, with which it is backward-compatible. It differs mainl in the factthat the bus is now $%-bits wide, and runs at higher fre&uencies 'now up to ()*+,compared to $$)*+ - the fastest PCI fre&uenc.

PCI-Express, on the other hand, uses a serial interconnect along a switched bus dedicatede!clusivel to that slot. In this respect, and most others, it uses radicall new architecture,

having little to do with old PCI. urthermore, PCI-!press has the uni&ue capabilit ofmultiplying up individual data "lanes", to produce aggregate interconnects that candeliver up to /$ times the bandwidth of a single lane. 0his is wh ou will alwas see PCI-!press slots referred to as "PCI-!press1%" or

S$S

,*e iconlo%o use& or SCSI8


10/27

Small $omputer System nter'ace/S$S= & - z i&SKUZ-ee0H1is a set o stan&ar&s orp*ysically connectin% an& transerrin% &ata between computers an&perip*eral &e'ices8,*e SCSI stan&ar&s &eine comman&s=protocols= an& electrical an& optical interaces8

SCSI is most commonly use& or *ar& &isks an& tape &ri'es= but it can connect a wi&e

ran%e o ot*er &e'ices= inclu&in% scanners an& CD&ri'es8,*e SCSI stan&ar& &eines

comman& sets or speciicperip*eral &e'ice typesJ t*e presence o :unknown: as one ot*ese types means t*at in t*eory it can be use& as an interace to almost any &e'ice= but

t*e stan&ar& is *i%*ly pra%matic an& a&&resse& towar& commercial reFuirements8

SCSI is an intelli%ent= perip*eral= buere&= peer to peer interace8 It *i&es t*e comple3ityo p*ysical ormat8 )'ery &e'ice attac*es to t*e SCSI bus in a similar manner8 $p to or

15 &e'ices can be attac*e& to a sin%le bus8 ,*ere can be any number o *osts an&

perip*eral &e'ices but t*ere s*oul& be at least one *ost8 SCSI uses *an& s*ake si%nalsbetween &e'ices= SCSI-1= SCSI-2 *a'e t*e option o parity error c*eckin%8 Startin% wit*

SCSI-$15 /part o SCSI-70 all comman&s an& &ata are error c*ecke& by a CRC72

c*ecksum8 ,*e SCSI protocol &eines communication rom *ost to *ost= *ost to a

perip*eral &e'ice= perip*eral &e'ice to a perip*eral &e'ice8 "owe'er most perip*eral&e'ices are e3clusi'ely SCSI tar%ets= incapable o actin% as SCSI initiatorsKunable to

initiate SCSI transactions t*emsel'es8 ,*ereore perip*eral-to-perip*eral communications

are uncommon= but possible in most SCSI applications8 ,*e Symbios Lo%ic7C1 c*ipis an e3ample o a PCI*ost interace t*at can act as a SCSI tar%et8

History

SCSI was &eri'e& rom :S+SI:= t*e :S*u%art +ssociatesSystem Interace:= &e'elope& c8

19> an& publicly &isclose& in 1918H2+ S+SI controller pro'i&e& a bri&%e between a*ar& &isk &ri'es low-le'el interace an& a *ost computer= w*ic* nee&e& to rea& blocks o

&ata8 S+SI controller boar&s were typically t*e si#e o a *ar& &isk &ri'e an& were usually

p*ysically mounte& to t*e &ri'es c*assis8 S+SI= w*ic* was use& in mini- an& earlymicrocomputers= &eine& t*e interace as usin% a -pin lat ribbon connector w*ic* was

a&opte& as t*e SCSI-1 connector8 S+SI is a ully compliant subset o SCSI-1 so t*at

many= i not all= o t*e t*en e3istin% S+SI controllers were SCSI-1 compatible8H7

Larry .ouc*eris consi&ere& to be t*e :at*er: o S+SI an& SCSI &ue to *is pioneerin%work irst at S*u%art +ssociatesan& t*en at +&aptec8H4

$ntil at least ?ebruary 192= +6SI &e'elope& t*e speciication as :S+SI: an& :S*u%art+ssociates System InteraceJ:H*owe'er= t*e committee &ocumentin% t*e stan&ar& woul&

not allow it to be name& ater a company8 +lmost a ull &ay was &e'ote& to a%reein% toname t*e stan&ar& :Small Computer System Interace=: w*ic* .ouc*er inten&e& to be

pronounce& :se3y:= but )6DLsH5Dal +llan pronounce& t*e new acronym as :scu##y:

an& t*at stuck8H4
http://en.wikipedia.org/wiki/Wikipedia:IPA_for_Englishhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_Englishhttp://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_keyhttp://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_keyhttp://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_keyhttp://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_keyhttp://en.wikipedia.org/wiki/#cite_note-0http://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/Interface_(computer_science)http://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/Optical_drivehttp://en.wikipedia.org/wiki/Optical_drivehttp://en.wikipedia.org/wiki/SCSI_Peripheral_Device_Typehttp://en.wikipedia.org/wiki/SCSI_Peripheral_Device_Typehttp://en.wikipedia.org/wiki/Cyclic_redundancy_checkhttp://en.wikipedia.org/wiki/SCSI_targethttp://en.wikipedia.org/wiki/SCSI_initiatorhttp://en.wikipedia.org/wiki/Symbios_Logichttp://en.wikipedia.org/wiki/Peripheral_Component_Interconnecthttp://en.wikipedia.org/wiki/Shugart_Associateshttp://en.wikipedia.org/wiki/#cite_note-1http://en.wikipedia.org/wiki/#cite_note-2http://en.wikipedia.org/w/index.php?title=Larry_Boucher&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Larry_Boucher&action=edit&redlink=1http://en.wikipedia.org/wiki/Shugart_Associateshttp://en.wikipedia.org/wiki/Shugart_Associateshttp://en.wikipedia.org/wiki/Adaptechttp://en.wikipedia.org/wiki/#cite_note-CHM-3http://en.wikipedia.org/wiki/#cite_note-ANSI-4http://en.wikipedia.org/wiki/#cite_note-5http://en.wikipedia.org/wiki/#cite_note-CHM-3http://en.wikipedia.org/wiki/Wikipedia:IPA_for_Englishhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Wikipedia:IPA_for_Englishhttp://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_keyhttp://en.wikipedia.org/wiki/#cite_note-0http://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/Interface_(computer_science)http://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/Optical_drivehttp://en.wikipedia.org/wiki/SCSI_Peripheral_Device_Typehttp://en.wikipedia.org/wiki/Cyclic_redundancy_checkhttp://en.wikipedia.org/wiki/SCSI_targethttp://en.wikipedia.org/wiki/SCSI_initiatorhttp://en.wikipedia.org/wiki/Symbios_Logichttp://en.wikipedia.org/wiki/Peripheral_Component_Interconnecthttp://en.wikipedia.org/wiki/Shugart_Associateshttp://en.wikipedia.org/wiki/#cite_note-1http://en.wikipedia.org/wiki/#cite_note-2http://en.wikipedia.org/w/index.php?title=Larry_Boucher&action=edit&redlink=1http://en.wikipedia.org/wiki/Shugart_Associateshttp://en.wikipedia.org/wiki/Adaptechttp://en.wikipedia.org/wiki/#cite_note-CHM-3http://en.wikipedia.org/wiki/#cite_note-ANSI-4http://en.wikipedia.org/wiki/#cite_note-5http://en.wikipedia.org/wiki/#cite_note-CHM-3


11/27

+ number o companies suc* as6CR Corporation=+&aptecan& ;ptimem were early

supporters o t*e SCSI stan&ar&8H,*e 6CR acility in (ic*ita= Aansasis wi&ely t*ou%*t

to *a'e &e'elope& t*e in&ustrys irst SCSI c*ipJ it worke& t*e irst time8H>

,*e :small: part in SCSI is *istoricalJ since t*e mi&-199s= SCSI *as been a'ailable on

e'en t*e lar%est o computer systems8

Since its stan&ar&i#ation in 195= SCSI *as been commonly use& in t*e +mi%a=+pple

!acintos*an& Sun !icrosystemscomputer lines an& PC ser'er systems8 +pple starte&usin% Parallel +,+/also known asIDE0 or its low-en& mac*ines wit* t*e !acintos*

Mua&ra57 in 1994= an& a&&e& it to its *i%*-en& &esktops startin% wit* t*e Power

!acintos* 7 in 199>8 +pple &roppe& on-boar& SCSI completely /in a'or o ID) an&?ire(ire0 wit* t*e /.lue G (*ite0 Power !ac 7 in 19998 Sun *as switc*e& its lower

en& ran%e to Serial +,+/S+,+08 SCSI *as ne'er been popular in t*e low-price& I.!

PC worl&= owin% to t*e lower cost an& a&eFuate perormance o +,+ *ar& &isk stan&ar&8

SCSI &ri'es an& e'en SCSI R+IDsbecame common in PC workstations or 'i&eo or

au&io pro&uction8

Recent 'ersions o SCSI K Serial Stora%e +rc*itecture/SS+0= SCSI-o'er-?ibre C*annel

Protocol/?CP0= Serial +ttac*e& SCSI/S+S0= +utomationDri'e Interace N ,ransport

Protocol /+D,0= an& $S. +ttac*e& SCSI /$+S0 K break rom t*e tra&itionalparallelSCSIstan&ar&s an& perorm &ata transer 'ia serial communications8 +lt*ou%* muc* o

t*e &ocumentation o SCSI talks about t*e parallel interace= most contemporary

&e'elopment eort is on serial SCSI8 Serial SCSI *as a number o a&'anta%es o'erparallel SCSIO aster &ata rates= *ot swappin%/some but not all parallel SCSI interaces

support it0= an& impro'e& ault isolation8 ,*e primary reason or t*e s*it to serial

interaces is t*e clock skewissue o *i%* spee& parallel interaces= w*ic* makes t*e aster

'ariants o parallel SCSI susceptible to problems cause& by cablin% an& termination8Serial SCSI &e'ices are more e3pensi'e t*an t*e eFui'alent parallel SCSI &e'ices= but

t*is is likely to c*an%e soonHcitation needed8

iS$Spreser'es t*e basic SCSIpara&i%m=especially t*e comman& set= almostunc*an%e&= t*rou%* embe&&in% o SCSI-7 o'er ,CPIP8

SCSI is popular on *i%*-perormance workstations an& ser'ers8 R+IDs on ser'ers almost

always use SCSI *ar& &isks= t*ou%* a number o manuacturers oer S+,+-base& R+ID

systems as a c*eaper option8 Desktop computers an& notebooks more typically use t*e+,+ID) or t*e newer S+,+ interaces or *ar& &isks= an& $S.= eS+,+= an& ?ire(ire

connections or e3ternal &e'ices8

SCSI is a'ailable in a 'ariety o interaces8 ,*e irst= still 'ery common= wasparallelSCSI/now also calle& SPI0= w*ic* uses aparallelelectrical bus&esi%n8 +s o 2= SPI

is bein% replace& by Serial +ttac*e& SCSI/S+S0= w*ic* uses a serial&esi%n but retains

ot*er aspects o t*e tec*nolo%y8 iSCSI&rops p*ysical implementation entirely= an&
http://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/Adaptechttp://en.wikipedia.org/wiki/Adaptechttp://en.wikipedia.org/wiki/#cite_note-ANSI-4http://en.wikipedia.org/wiki/Wichita,_Kansashttp://en.wikipedia.org/wiki/#cite_note-6http://en.wikipedia.org/wiki/Amigahttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Sun_Microsystemshttp://en.wikipedia.org/wiki/Parallel_ATAhttp://en.wikipedia.org/wiki/Parallel_ATAhttp://en.wikipedia.org/wiki/Macintosh_Quadrahttp://en.wikipedia.org/wiki/Macintosh_Quadrahttp://en.wikipedia.org/wiki/Macintosh_Quadrahttp://en.wikipedia.org/wiki/FireWirehttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/RAIDhttp://en.wikipedia.org/wiki/Serial_Storage_Architecturehttp://en.wikipedia.org/wiki/Serial_Storage_Architecturehttp://en.wikipedia.org/wiki/Fibre_Channel_Protocolhttp://en.wikipedia.org/wiki/Fibre_Channel_Protocolhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Hot_swappinghttp://en.wikipedia.org/wiki/Hot_swappinghttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Paradigmhttp://en.wikipedia.org/wiki/Paradigmhttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_communicationshttp://en.wikipedia.org/wiki/Electrical_bushttp://en.wikipedia.org/wiki/Electrical_bushttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Serial_communicationshttp://en.wikipedia.org/wiki/Serial_communicationshttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/Adaptechttp://en.wikipedia.org/wiki/#cite_note-ANSI-4http://en.wikipedia.org/wiki/Wichita,_Kansashttp://en.wikipedia.org/wiki/#cite_note-6http://en.wikipedia.org/wiki/Amigahttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Sun_Microsystemshttp://en.wikipedia.org/wiki/Parallel_ATAhttp://en.wikipedia.org/wiki/Macintosh_Quadrahttp://en.wikipedia.org/wiki/Macintosh_Quadrahttp://en.wikipedia.org/wiki/FireWirehttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/RAIDhttp://en.wikipedia.org/wiki/Serial_Storage_Architecturehttp://en.wikipedia.org/wiki/Fibre_Channel_Protocolhttp://en.wikipedia.org/wiki/Fibre_Channel_Protocolhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Hot_swappinghttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Paradigmhttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/Parallel_communicationshttp://en.wikipedia.org/wiki/Electrical_bushttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Serial_communicationshttp://en.wikipedia.org/wiki/ISCSI


12/27

instea& uses ,CPIPas a transport mec*anism8 !any ot*er interaces w*ic* &o not rely

on complete SCSI stan&ar&s still implement t*eSCSI comman& protocol8

SCSI interaces *a'e oten been inclu&e& on computers rom 'arious manuacturers oruse un&er !icrosot (in&ows=!ac ;S=$ni3an&Linu3operatin% systems= eit*er

implemente& on t*e mot*erboar&or by t*e means o plu%-in a&aptors8 (it* t*e a&'ent oS+San& S+,+&ri'es= pro'ision or SCSI on mot*erboar&s is bein% &iscontinue&8 + ew

companies still market SCSI interaces or mot*erboar&s supportin% PCIe an& PCI-X8

Parallel S$S

nter'aceAlternative

names

Speci'ication

documentH$onnector

idt%

)bits+$loc2H9

!a"im

Bandwidt%

)!B/s+ H1Bandwidt%

)!bit/s+ H11

(en#

)sin

ended

SCSI-1 6arrowSCSI SCSI-1/1950 H1

IDCJ

CentronicsC

!"# !.s 4 !bits 5 m

?ast SCSISCSI-2/19940

IDCJCentronics

C

1 !"# 1 !.s !bits 7 m

?ast-(i&eSCSI

SCSI-2JSCSI-7 SPI

/19950 H1

2 3 -pin

/SCSI-20J1 3 5-pin

/SCSI-70

15 1 !"# 2 !.s 15 !bits 7 m

$ltraSCSI

?ast-2SCSI-7 SPIH1 IDC 2 !"# 2 !.s 15 !bits

18 m

7 m

$ltra

(i&e

SCSI

SCSI-7 SPIH1 5-pin 15 2 !"# 4 !.s 72 !bits

6+

18 m

7 m

$ltra2

SCSI?ast-4

SCSI-7 SPI-2

/199>0-pin 4 !"# 4 !.s 72 !bits 6+

$ltra2(i&e

SCSI

SCSI-7 SPI-2

5-pinJ -

pin/SC+SC+-

20

15 4 !"# !.s 54 !bits 6+

$ltra7SCSI

$ltra-15J?ast-

wi&e

SCSI-7 SPI-7/19990 H1

5-pinJ -

pin/SC+SC+-

20

15 4 !"#DDR

15 !.s 12 !bits 6+

$ltra-72

SCSI

$ltra-4J

?ast-15

SCSI-7 SPI-4

/220 H1

5-pinJ -pin

/SC+SC+-

20

15 !"#

DDR72 !.s 25 !bits 6+

$ltra-54 $ltra- SCSI-7 SPI- 5-pinJ - 15 15 !"# 54 !.s 12 !bits
http://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/#SCSI_command_protocolhttp://en.wikipedia.org/wiki/#SCSI_command_protocolhttp://en.wikipedia.org/wiki/#SCSI_command_protocolhttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://en.wikipedia.org/wiki/Mac_OShttp://en.wikipedia.org/wiki/Mac_OShttp://en.wikipedia.org/wiki/Mac_OShttp://en.wikipedia.org/wiki/Unixhttp://en.wikipedia.org/wiki/Unixhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Motherboardhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/#cite_note-7http://en.wikipedia.org/wiki/#cite_note-7http://en.wikipedia.org/wiki/#cite_note-clock-8http://en.wikipedia.org/wiki/MB/shttp://en.wikipedia.org/wiki/#cite_note-megabyte-9http://en.wikipedia.org/wiki/Mbit/shttp://en.wikipedia.org/wiki/#cite_note-megabit-10http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/Double_data_ratehttp://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/#SCSI_command_protocolhttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://en.wikipedia.org/wiki/Mac_OShttp://en.wikipedia.org/wiki/Unixhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Motherboardhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/#cite_note-7http://en.wikipedia.org/wiki/#cite_note-clock-8http://en.wikipedia.org/wiki/MB/shttp://en.wikipedia.org/wiki/#cite_note-megabyte-9http://en.wikipedia.org/wiki/Mbit/shttp://en.wikipedia.org/wiki/#cite_note-megabit-10http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/Double_data_ratehttp://en.wikipedia.org/wiki/#cite_note-specwithdrawn-14http://en.wikipedia.org/wiki/Single_Connector_Attachment


13/27

SCSI /270 pin DDR

,t%er S$S inter'aces

nter'ace Alternativenames Speci'icationdocument $onnector idt%)bits+ $loc2H9

!a"imum

T%rou#%put)!B/s+H1

T%rou#%put)!bit/s+H11

(

SS+ 1 2 !"# 4 !.sH1>H1 72 !bits 2 m

SS+ 4 1 4 !"# !.sH1>H1 54 !bits 2 m

?C-+L

1b1 1 "#

1 !.sH1

H19 !bits m

?C-+L2b

1 2 "#2 !.sH1

H19 15 !bits m

?C-+L

4b1 4 "#

4 !.sH1

H19 72 !bits m

S+S 1 7 "# 7 !.sH1

H19 24 !bits 5 m

iSCSI Implementation- an& network-&epen&ent

Traditional S$S Parallel nter'ace

Internal parallel SCSI cables are usually ribbons= wit* two or more = 5= or pinconnectors attac*e&8 )3ternal cables are typically s*iel&e& /but may not be0= wit* or

59pin connectors at eac* en&= &epen&in% upon t*e speciic SCSI bus wi&t* supporte&8H22

,*e pin Sin%le Connector +ttac*ment/SC+0 is typically use& or *ot-plu%%able

&e'ices= w*ere e3ternal cables are not usually reFuire&8

Serial attac%ed S$S

Serial attac*e& SCSIuses a mo&iie&Serial +,+&ata an& power cable8

iS$S

iSCSI/Internet Small Computer System Interace0 usually uses )t*ernetconnectors an&cables as its p*ysical transport= but can run o'er any p*ysical transport capable o

transportin% IP8

USB Attac%ed S$S

$S. +ttac*e& SCSIallows SCSI &e'ices to use t*e $ni'ersal Serial .us8

Automation/Drive nter'ace
http://en.wikipedia.org/wiki/#cite_note-clock-8http://en.wikipedia.org/wiki/#cite_note-megabyte-9http://en.wikipedia.org/wiki/#cite_note-megabit-10http://en.wikipedia.org/wiki/Serial_Storage_Architecturehttp://en.wikipedia.org/wiki/#cite_note-spatial_reuse-16http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-spatial_reuse-16http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/FC-ALhttp://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/Serial_attached_SCSIhttp://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Ribbon_cableshttp://en.wikipedia.org/wiki/#cite_note-21http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/Serial_attached_SCSIhttp://en.wikipedia.org/wiki/Serial_attached_SCSIhttp://en.wikipedia.org/wiki/Serial_Attached_SCSI#Connectorshttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Internet_Protocolhttp://en.wikipedia.org/wiki/USB_Attached_SCSIhttp://en.wikipedia.org/wiki/Universal_Serial_Bushttp://en.wikipedia.org/wiki/#cite_note-clock-8http://en.wikipedia.org/wiki/#cite_note-megabyte-9http://en.wikipedia.org/wiki/#cite_note-megabit-10http://en.wikipedia.org/wiki/Serial_Storage_Architecturehttp://en.wikipedia.org/wiki/#cite_note-spatial_reuse-16http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-spatial_reuse-16http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/FC-ALhttp://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/Serial_attached_SCSIhttp://en.wikipedia.org/wiki/#cite_note-fdx-17http://en.wikipedia.org/wiki/#cite_note-per_dir-18http://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Ribbon_cableshttp://en.wikipedia.org/wiki/#cite_note-21http://en.wikipedia.org/wiki/Single_Connector_Attachmenthttp://en.wikipedia.org/wiki/Serial_attached_SCSIhttp://en.wikipedia.org/wiki/Serial_Attached_SCSI#Connectorshttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Internet_Protocolhttp://en.wikipedia.org/wiki/USB_Attached_SCSIhttp://en.wikipedia.org/wiki/Universal_Serial_Bus


14/27

,*e +utomationDri'e Interace N ,ransport Protocol /+D,0 is use& to connect

remo'able me&ia &e'ices= suc* as tape &ri'es= wit* t*e controllers o t*e libraries

/automation &e'ices0 in w*ic* t*ey are installe&8 ,*e +DI stan&ar& speciies t*e use oRS-422or t*e p*ysical connections8 ,*e secon&-%eneration +D,-2 stan&ar& &eines

i+D,= use o t*e +D, protocol o'er IP /Internet Protocol0 connections= suc* as o'er

)t*ernet8 ,*e +utomationDri'e Interace N Comman&s stan&ar&s /+DC= +DC-2= an&+DC-70 &eine SCSI comman&s or t*ese installations8

S$S command protocol

!ain articleO SCSI comman&

In a&&ition to many &ierent *ar&ware implementations= t*e SCSI stan&ar&s also inclu&ea comple3 set o comman& protocol &einitions8 ,*e SCSI comman& arc*itecture was

ori%inally &eine& orparallel SCSIbuses but *as been carrie& orwar& wit* minimal

c*an%e or use wit* iSCSI an& serial SCSI8 ;t*er tec*nolo%ies w*ic* use t*e SCSI

comman& set inclu&e t*e+,+ Packet Interace= $S. !ass Stora%e classan& ?ire(ireS.P-28

In SCSI terminolo%y= communication takes place between an initiatoran& atar%et8 ,*e

initiator sen&s a comman&to t*e tar%et w*ic* t*en respon&s8 SCSI comman&s are sent in

a Comman& Descriptor .lock /CD.08 ,*e CD. consists o a one byte operation co&eollowe& by i'e or more bytes containin% comman&-speciic parameters8

+t t*e en& o t*e comman& seFuence t*e tar%et returns aStatus Co&ebyte w*ic* is

usually * or success= 2* or an error /calle& a C*eck Con&ition0= or * or busy8(*en t*e tar%et returns a C*eck Con&ition in response to a comman&= t*e initiator

usually t*en issues a SCSI ReFuest Sense comman&in or&er to obtain a Aey Co&eMualiier /ACM0 rom t*e tar%et8 ,*e C*eck Con&ition an& ReFuest Sense seFuence

in'ol'es a special SCSI protocol calle& aContin%ent +lle%iance Con&ition8

,*ere are 4 cate%ories o SCSI comman&sO 6 /non-&ata0= ( /writin% &ata rom initiator

to tar%et0= R /rea&in% &ata0= an& . /bi&irectional08 ,*ere are about 5 &ierent SCSI

comman&sin total= wit* t*e most common bein%O

,est unit rea&yO Mueries &e'ice to see i it is rea&y or &ata transers /&isk spun

up= me&ia loa&e&= etc808

InFuiryO Returns basic &e'ice inormation= also use& to :pin%: t*e &e'ice since it

&oes not mo&iy sense &ata8 ReFuest senseO Returns any error co&es rom t*e pre'ious comman& t*at returne&

an error status8

Sen& &ia%nostic an& Recei'e &ia%nostic resultsO runs a simple sel-test= or a

specialise& test &eine& in a &ia%nostic pa%e8

StartStop unitO Spins &isks up an& &own= loa&unloa& me&ia8

Rea& capacityO Returns stora%e capacity8
http://en.wikipedia.org/wiki/RS-422http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/ATAPIhttp://en.wikipedia.org/wiki/ATAPIhttp://en.wikipedia.org/wiki/USB_mass_storage_device_classhttp://en.wikipedia.org/wiki/Serial_Bus_Protocol_2http://en.wikipedia.org/wiki/Serial_Bus_Protocol_2http://en.wikipedia.org/wiki/SCSI_initiatorhttp://en.wikipedia.org/wiki/SCSI_targethttp://en.wikipedia.org/wiki/SCSI_targethttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_CDBhttp://en.wikipedia.org/wiki/SCSI_Status_Codehttp://en.wikipedia.org/wiki/SCSI_Status_Codehttp://en.wikipedia.org/wiki/SCSI_Status_Codehttp://en.wikipedia.org/wiki/SCSI_check_conditionhttp://en.wikipedia.org/wiki/SCSI_Request_Sense_Commandhttp://en.wikipedia.org/wiki/KCQhttp://en.wikipedia.org/wiki/SCSI_contingent_allegiance_conditionhttp://en.wikipedia.org/wiki/SCSI_contingent_allegiance_conditionhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_Test_Unit_Ready_Commandhttp://en.wikipedia.org/wiki/SCSI_Inquiry_Commandhttp://en.wikipedia.org/wiki/SCSI_Request_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_Send_Diagnostic_Commandhttp://en.wikipedia.org/wiki/SCSI_Receive_Diagnostic_Results_Commandhttp://en.wikipedia.org/wiki/SCSI_diagnostic_pageshttp://en.wikipedia.org/wiki/SCSI_Start_Stop_Unit_Commandhttp://en.wikipedia.org/wiki/SCSI_Read_Capacity_Commandhttp://en.wikipedia.org/wiki/RS-422http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/Parallel_SCSIhttp://en.wikipedia.org/wiki/ATAPIhttp://en.wikipedia.org/wiki/USB_mass_storage_device_classhttp://en.wikipedia.org/wiki/Serial_Bus_Protocol_2http://en.wikipedia.org/wiki/Serial_Bus_Protocol_2http://en.wikipedia.org/wiki/SCSI_initiatorhttp://en.wikipedia.org/wiki/SCSI_targethttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_CDBhttp://en.wikipedia.org/wiki/SCSI_Status_Codehttp://en.wikipedia.org/wiki/SCSI_check_conditionhttp://en.wikipedia.org/wiki/SCSI_Request_Sense_Commandhttp://en.wikipedia.org/wiki/KCQhttp://en.wikipedia.org/wiki/SCSI_contingent_allegiance_conditionhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_commandhttp://en.wikipedia.org/wiki/SCSI_Test_Unit_Ready_Commandhttp://en.wikipedia.org/wiki/SCSI_Inquiry_Commandhttp://en.wikipedia.org/wiki/SCSI_Request_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_Send_Diagnostic_Commandhttp://en.wikipedia.org/wiki/SCSI_Receive_Diagnostic_Results_Commandhttp://en.wikipedia.org/wiki/SCSI_diagnostic_pageshttp://en.wikipedia.org/wiki/SCSI_Start_Stop_Unit_Commandhttp://en.wikipedia.org/wiki/SCSI_Read_Capacity_Command


15/27

?ormat unitO Sets all sectors to all #eroes= also allocates lo%ical blocks a'oi&in%

&eecti'e sectors8

SCSI Rea& ormat capacitiesO Retrie'e t*e &ata capacity o t*e &e'ice8

Rea& /our 'ariants0O Rea&s &ata rom a &e'ice8

(rite /our 'ariants0O (rites &ata to a &e'ice8

Lo% senseO Returns current inormation rom lo% pa%es8 !o&e senseO Returns current &e'ice parameters rom mo&e pa%es8

!o&e selectO Sets &e'ice parameters in a mo&e pa%e8

)ac* &e'ice on t*e SCSI bus is assi%ne& a uniFue SCSI i&entiication number or ID8

De'ices may encompass multiple lo%ical units= w*ic* are a&&resse& by lo%ical unit

number/L$608 Simple &e'ices *a'e Qust one L$6= more comple3 &e'ices may *a'emultiple L$6s8

+ :&irect access: /i8e8 &isk type0 stora%e &e'ice consists o a number o lo%ical blocks=

usually reerre& to by t*e term Lo%ical .lock +&&ress /L.+08 + typical L.+ eFuates to

12 bytes o stora%e8 ,*e usa%e o L.+s *as e'ol'e& o'er time an& so our &ierentcomman& 'ariants are pro'i&e& or rea&in% an& writin% &ata8 ,*e Rea&/50an& (rite/50

comman&s contain a 21-bit L.+ a&&ress8 ,*e Rea&/10=Rea&/120=Rea& Lon%=

(rite/10=(rite/120= an& (rite Lon%comman&s all contain a 72-bit L.+ a&&ress plus'arious ot*er parameter options8

+ :seFuential access: /i8e8 tape-type0 &e'ice &oes not *a'e a speciic capacity because it

typically &epen&s on t*e len%t* o t*e tape= w*ic* is not known e3actly8 Rea&s an& writes

on a seFuential access &e'ice *appen at t*e current position= not at a speciic L.+8 ,*eblock si#e on seFuential access &e'ices can eit*er be i3e& or 'ariable= &epen&in% on t*e

speciic &e'ice8 ,ape &e'ices suc* as *al-inc* 9-track tape= DDS/4 mm tapes p*ysically

similar to D+,0= )3abyte= etc8= support 'ariable block si#es8

How Parallel S$S wor2s

,*is section does not citeany re'erences or sources8Please *elp impro'e t*is section by a&&in% citations toreliable sources8 $nsource& material may be

c*allen%e&an& remo'e&8 (June 2008)

SCSI uses a protocol met*o& to transer &ata between &e'ices on t*e bus8 It is a circularprocess w*ic* starts an& en&s up in t*e same layer8 ?rom t*e irst layer= all a&&itional

layers o protocol must be e3ecute& beore any &ata is transerre& to or rom anot*er

&e'ice an& t*e layers o protocol must be complete& ater t*e &ata *as been transerre& tot*e en& o t*e process8 ,*e protocol layers are reerre& to as :SCSI bus p*ases:8 ,*ese

p*ases areO

.$S ?R))

+R.I,R+,I;6

S)L)C,I;6
http://en.wikipedia.org/wiki/SCSI_Format_Unit_Commandhttp://en.wikipedia.org/w/index.php?title=SCSI_Read_format_capacities&action=edit&redlink=1http://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Log_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_log_pageshttp://en.wikipedia.org/wiki/SCSI_Mode_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_mode_pageshttp://en.wikipedia.org/wiki/SCSI_Mode_Select_Commandhttp://en.wikipedia.org/wiki/Logical_unit_numberhttp://en.wikipedia.org/wiki/Logical_unit_numberhttp://en.wikipedia.org/wiki/SCSI_LBAhttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/IBM_9_trackhttp://en.wikipedia.org/wiki/Digital_Data_Storagehttp://en.wikipedia.org/wiki/Digital_audio_tapehttp://en.wikipedia.org/wiki/Exabyte_(company)http://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/SCSI_Format_Unit_Commandhttp://en.wikipedia.org/w/index.php?title=SCSI_Read_format_capacities&action=edit&redlink=1http://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Log_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_log_pageshttp://en.wikipedia.org/wiki/SCSI_Mode_Sense_Commandhttp://en.wikipedia.org/wiki/SCSI_mode_pageshttp://en.wikipedia.org/wiki/SCSI_Mode_Select_Commandhttp://en.wikipedia.org/wiki/Logical_unit_numberhttp://en.wikipedia.org/wiki/Logical_unit_numberhttp://en.wikipedia.org/wiki/SCSI_LBAhttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Read_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/SCSI_Write_Commandshttp://en.wikipedia.org/wiki/IBM_9_trackhttp://en.wikipedia.org/wiki/Digital_Data_Storagehttp://en.wikipedia.org/wiki/Digital_audio_tapehttp://en.wikipedia.org/wiki/Exabyte_(company)http://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence


16/27

!)SS+) ;$,

C;!!+6D ;$,

D+,+ ;$,I6

S,+,$S I6

!)SS+) I6

R)S)L)C,I;6

,*e SCSI bus can be in only one p*ase at a %i'en time8

6ot all controllers use all t*e p*ases an& a well written &ri'er will not assume t*at p*ases

will occur but rat*er comman& an operation t*en rea& status to &etermine t*e p*ase t*att*e &e'ice wants to &o ne3t8 ,*is tec*niFue allows a sin%le &ri'er to work wit* a 'ariety

o controllers t*at may 'ary in w*et*er t*ey &rop unnee&e& p*ases or not8 In early

implementations o SCSI= writin% a sin%le &ri'er to work wit* Xebec an& D,C reFuire&t*is approac* &e'elope& by Dou%las oo&all w*ile a&&in% SCSI support to t*e +mpro

Little .oar& 8

Data si%nals in parallell SCSIOH27D./->0 D./P0 ,)R!P(R +,6 .S +CA RS,

!S S)L CD R)M I;

,*e sin%le en&e& SCSI .us lines *as a c*aracteristic impe&anceo 172 T8 Data transer

is perorme& by t*e transmitter setup &ata si%nals D.->=D.P8 ,*en acti'ate R)M= await

+CA= an& repeat t*e seFuence8H27

SuperSpeed USB 'rom t%e USB-F

+s tec*nolo%y inno'ation marc*es orwar&= new kin&s o &e'ices= me&ia ormats= an& lar%e

ine3pensi'e stora%e are con'er%in%8 ,*ey reFuire si%niicantly more bus ban&wi&t* tomaintain t*e interacti'e e3perience users *a'e come to e3pect8 In a&&ition= user applications

&eman& a *i%*er perormance connection between t*e PC an& t*ese increasin%ly

sop*isticate& perip*erals8 $S. 78 a&&resses t*is nee& by a&&in% an e'en *i%*er transer

rate to matc* t*ese new usa%e an& &e'ices8

$S. continues to be t*e answer to connecti'ity or PC= Consumer )lectronics= an& !obile

arc*itectures8 It is a ast= bi&irectional= low-cost= &ynamically attac*able interace t*at is

consistent wit* t*e reFuirements o t*e PC platorms o to&ay an& tomorrow8

SuperSpee& $S. brin%s si%niicant perormance en*ancements to t*e ubiFuitous $S.

stan&ar&= w*ile remainin% compatible wit* t*e billions o $S. enable& &e'ices currently
http://en.wikipedia.org/wiki/#cite_note-m309x-22http://en.wikipedia.org/wiki/Characteristic_impedancehttp://en.wikipedia.org/wiki/#cite_note-m309x-22http://en.wikipedia.org/wiki/#cite_note-m309x-22http://en.wikipedia.org/wiki/#cite_note-m309x-22http://en.wikipedia.org/wiki/Characteristic_impedancehttp://en.wikipedia.org/wiki/#cite_note-m309x-22


17/27

&eploye& in t*e market8 SuperSpee& $S. will &eli'er 13 t*e &ata transer rate o "i-Spee&

$S.= as well as impro'e& power eiciency8

SuperSpee! USB *- . $"p- -ignling rte o55ering 17 per5ormn?e in?re-e o>er Hi0Spee! USB3

SuperSpee! USB i- Sn?0'0$o te?*nolog t*t minimize- u-er it0time3

SuperSpee! USB ill pro>i!e ptimize! Poer %55i?ien?3'o !e>i?e polling n! loer?ti>e n! i!le poer re;uirement-3

SuperSpee! USB i- "?r!- ?ompti"le it* USB 2373 De>i?e- interoperte it* USB237 plt5orm-3 Ho-t- -upport USB 237 leg? !e>i?e-3

T%e USB system

+ $S. system *as an asymmetric&esi%n= consistin% o a *ost= a multitu&e o &ownstream

$S. ports= an& multipleperip*eral &e'icesconnecte& in a tiere&-star topolo%y8+&&itional $S. *ubsmay be inclu&e& in t*e tiers= allowin% branc*in% into a tree

structure wit* up to i'e tier le'els8 + $S. *ost may *a'e multiple *ost controllers an&

eac* *ost controller may pro'i&e one or more $S. ports8 $p to 12> &e'ices= inclu&in%*ub &e'ices i present= may be connecte& to a sin%le *ost controller8H11H12

$S. &e'ices are linke& in series t*rou%* hubs8 ,*ere always e3ists one *ub known as t*e

root *ub= w*ic* is built into t*e *ost controller8

So-calle&sharing hubs= w*ic* allow multiple computers to access t*e same perip*eral&e'ice/s0= also e3ist an& work by switc*in% access between PCs= eit*er automatically or

manually8 S*arin% *ubs are popular in small-oice en'ironments8 In network terms= t*ey

con'er%e rat*er t*an &i'er%e branc*es8Hcitation needed

+ p*ysical $S. &e'ice may consist o se'eral lo%ical sub-&e'ices t*at are reerre& to asdevice functions8 + sin%le &e'ice may pro'i&e se'eral unctions= or e3ample= a webcam

/'i&eo &e'ice unction0 wit* a built-in microp*one /au&io &e'ice unction08 Suc* a &e'ice

is calle& a compound devicein w*ic* eac* lo%ical &e'ice is assi%ne& a &istincti'e a&&ress

by t*e *ost an& all lo%ical &e'ices are connecte& to a built-in *ub to w*ic* t*e p*ysical$S. wire is connecte&8 + *ost assi%ns one an& only one &e'ice a&&ress to a unction8

$S. en&points actually resi&e on t*e connecte& &e'iceO t*e c*annels to t*e *ost are

reerre& to as pipes8

$S. &e'ice communication is base& onpipes/lo%ical c*annels08 + pipe is a connection

rom t*e *ost controller to a lo%ical entity= oun& on a &e'ice= an& name& anendpoint8.ecause pipes correspon& 1-to-1 to en&points= t*e terms are sometimes use&

interc*an%eably8 + $S. &e'ice can *a'e up to 72 en&pointsO 15 into t*e *ost controller

an& 15 out o t*e *ost controller8 ,*e $S. stan&ar& reser'es one en&point o eac* type=
http://en.wikipedia.org/wiki/Symmetryhttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/Star_networkhttp://en.wikipedia.org/wiki/USB_hubhttp://en.wikipedia.org/wiki/#cite_note-10http://en.wikipedia.org/wiki/#cite_note-10http://en.wikipedia.org/wiki/#cite_note-11http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Webcamhttp://en.wikipedia.org/wiki/Webcamhttp://en.wikipedia.org/wiki/Communication_endpointhttp://en.wikipedia.org/wiki/Communication_endpointhttp://en.wikipedia.org/wiki/Symmetryhttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/Peripheral_devicehttp://en.wikipedia.org/wiki/Star_networkhttp://en.wikipedia.org/wiki/USB_hubhttp://en.wikipedia.org/wiki/#cite_note-10http://en.wikipedia.org/wiki/#cite_note-11http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Webcamhttp://en.wikipedia.org/wiki/Communication_endpoint


18/27

lea'in% a t*eoretical ma3imum o 7 or normal use8 $S. &e'ices sel&om *a'e t*is many

en&points8

,*ere are two types o pipesO stream an& messa%e pipes &epen&in% on t*e type o &atatranser8

isochronous transfersO at some %uarantee& &ata rate /oten= but not necessarily= as

ast as possible0 but wit* possible &ata loss /e8%8 realtime au&io or 'i&eo08

interrupt transfersO &e'ices t*at nee& %uarantee& Fuick responses /boun&e&

latency0 /e8%8 pointin% &e'ices an& keyboar&s08 bulk transfersO lar%e spora&ic transers usin% all remainin% a'ailable ban&wi&t*=

but wit* no %uarantees on ban&wi&t* or latency /e8%8 ile transers08

control transfersO typically use& or s*ort= simple comman&s to t*e &e'ice= an& a

status response= use&= or e3ample= by t*e bus control pipe number 8

+ stream pipe is a uni-&irectional pipe connecte& to a uni-&irectional en&point t*at

transers &ata usin% an isochronous= interrupt= or bulktranser8 + messa%e pipe is a bi-&irectional pipe connecte& to a bi-&irectional en&point t*at is e3clusi'ely use& or control&ata low8 +n en&point is built into t*e $S. &e'ice by t*e manuacturer an& t*ereore

e3ists permanently8 +n en&point o a pipe is a&&ressable wit* tuple (device_address

endpoint_number)as speciie& in a ,;A)6 packet t*at t*e *ost sen&s w*en it wants to

start a &ata transer session8 I t*e &irection o t*e &ata transer is rom t*e *ost to t*een&point= an ;$, packet /a speciali#ation o a ,;A)6 packet0 *a'in% t*e &esire& &e'ice

a&&ress an& en&point number is sent by t*e *ost8 I t*e &irection o t*e &ata transer is

rom t*e &e'ice to t*e *ost= t*e *ost sen&s an I6 packet instea&8 I t*e &estinationen&point is a uni-&irectional en&point w*ose manuacturers &esi%nate& &irection &oes not

matc* t*e ,;A)6 packet /e8%8= t*e manuacturers &esi%nate& &irection is I6 w*ile t*e

,;A)6 packet is an ;$, packet0= t*e ,;A)6 packet will be i%nore&8 ;t*erwise= it willbe accepte& an& t*e &ata transaction can start8 + bi-&irectional en&point= on t*e ot*er

*an&= accepts bot* I6 an& ;$, packets8

,wo $S. receptacles on t*e ront o a computer8

)n&points are %roupe& into interfacesan& eac* interace is associate& wit* a sin%le&e'ice unction8 +n e3ception to t*is is en&point #ero= w*ic* is use& or &e'ice

coni%uration an& w*ic* is not associate& wit* any interace8 + sin%le &e'ice unction

compose& o in&epen&ently controlle& interaces is calle& a composite device8 +

composite &e'ice only *as a sin%le &e'ice a&&ress because t*e *ost only assi%ns a &e'icea&&ress to a unction8

(*en a $S. &e'ice is irst connecte& to a $S. *ost= t*e $S. &e'ice enumeration

process is starte&8 ,*e enumeration starts by sen&in% a reset si%nal to t*e $S. &e'ice8,*e &ata rate o t*e $S. &e'ice is &etermine& &urin% t*e reset si%nalin%8 +ter reset= t*e

$S. &e'ices inormation is rea& by t*e *ost an& t*e &e'ice is assi%ne& a uniFue >-bit

a&&ress8 I t*e &e'ice is supporte& by t*e *ost= t*e &e'ice &ri'ers nee&e& or


19/27

communicatin% wit* t*e &e'ice are loa&e& an& t*e &e'ice is set to a coni%ure& state8 I

t*e $S. *ost is restarte&= t*e enumeration process is repeate& or all connecte& &e'ices8

,*e *ost controller &irects traic low to &e'ices= so no $S. &e'ice can transer any &ataon t*e bus wit*out an e3plicit reFuest rom t*e *ost controller8 In $S. 28= t*e *ost

controllerpollst*e bus or traic= usually in a roun&-robinas*ion8 ,*e slowest &e'iceconnecte& to a controller sets t*e ban&wi&t* o t*e interace8 ?or !uper!peed "!#

/&eine& since $S. 780= connecte& &e'ices can reFuest ser'ice rom *ost8 .ecause t*ereare two separate controllers in eac* $S. 78 *ost= $S. 78 &e'ices will transmit an&

recei'e at $S. 78 &ata rates re%ar&less o $S. 28 or earlier &e'ices connecte& to t*at

*ost8 ;peratin% &ata rates or t*em will be set in t*e le%acy manner8

LTO Tape Drives

NativeCapacity

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*P 2torage3orks 405 ( #67 ull

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http://en.wikipedia.org/wiki/Polling_(computer_science)http://en.wikipedia.org/wiki/Round-robin_schedulinghttp://en.wikipedia.org/wiki/Round-robin_schedulinghttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO4_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO4_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO4_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2350_Tape_Drive_Express.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2250_Tape_Drive_Express.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2340_Tape_Drive_Express_Model.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2240_Tape_Drive_Express.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Tape%20Drives/Quantum%20ATL/Quantum_DLT_S4.htmhttp://en.wikipedia.org/wiki/Polling_(computer_science)http://en.wikipedia.org/wiki/Round-robin_schedulinghttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO5_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO4_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/HP/HP_LTO4_Tape_Drives.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2350_Tape_Drive_Express.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2350_Tape_Drive_Express.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2250_Tape_Drive_Express.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2340_Tape_Drive_Express_Model.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2340_Tape_Drive_Express_Model.htmhttp://www.sunstarco.com/Tape%20Drives/IBM/IBM_TS2240_Tape_Drive_Express.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Default.htmhttp://www.sunstarco.com/Tape%20Drives/Quantum%20ATL/Quantum_DLT_S4.htm


20/27

2840 $7777;9 at$)9:s

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21/27

Durin% t*e secon& *al o 1999= tape users will *ear muc* about t*e merits o two

competin% tape ormats= Super Di%ital Linear ,ape /SDL,0 an& Linear ,ape ;pen/L,;08 + si%niicant &ierence in t*e implementation o t*ese two ormats can be oun&

in t*e track-ollowin% ser'o system= t*e mec*anism responsible or enablin% t*ee3tremely *i%* capacities &esire& by tape customers8 (*ile t*e optical trackin% tec*niFuebein% implemente& on SDL, is still in a &e'elopment p*ase= t*is article will attempt to

contrast t*e merits o t*e two track-ollowin% ser'o systems use& by SDL, an& L,; tape

ormats8 Anowin% more about t*e &ierences between t*e two ormats will *elp tapecustomers to make more inorme& an& e&ucate& c*oices w*en up%ra&in% current systems

or in'estin% in new ones8

In linear tape recor&in%= &ata is written on many a&Qacent tracks t*at run parallel to t*e

e&%e o t*e tape8 $sin% Di%ital Linear ,ape /DL,0 tec*nolo%y= it *as been possible topus* t*is tec*nolo%y to recor& 2 tracks across a one-*al-inc* tape= allowin% eac* tape

to store up to 7.8 "owe'er= to ac*ie'e ne3t %eneration tape capacities o 1. an&%reater= si%niicantly more tracks must be written on t*e me&ia8 ,ape en%ineers

reco%ni#e& t*e nee& or a track-ollowin% ser'o= a mec*anism t*at allows a tape *ea& to&ynamically ollow a tape track= because track positions luctuate &ue to sli%*t me&ia

'ariations= mec*anical tolerances= an& ot*er en'ironmental actors8

,*e track-ollowin% ser'o is crucial to reali#in% t*e ull capacity o tape stora%e solutionsan& ac*ie'in% reliable &ata stora%e8 + ser'o is similar to a cars cruise control= w*ic*

allows t*e car to automatically maintain a constant spee&8 ,*e cars ser'o compares t*e

actual 'elocity a%ainst t*e &esire& spee& an& re%ulates t*e accelerator accor&in%ly8

Similarly= a tape &ri'e usin% a track-ollowin% ser'o will constantly mo'e t*e *ea&= t*e

component t*at actually perorms t*e rea& an& write unction= an& ali%n it to t*e &esire&track8

,*ree years a%o= I.! intro&uce& t*e !a%star 79 tape &ri'e= a mainrame stora%epro&uct t*at uses tape wit* pre-written reerence tracks to %ui&e t*e track-ollowin%

ser'o8 Returnin% to t*e automobile metap*or= reerence tracks are like lane markers on a

roa&8 ,*ey pro'i&e t*e &ri'er wit* a continuous reerence as to w*ere t*e car s*oul& bepositione&8 Similarly= on a tape &ri'e= t*e *ea& *as special sensors t*at monitor t*e

reerence tracks8 I t*e sensors &etect t*e *ea& mo'in% o t*e track= t*e ser'o will

automatically mo'e t*e *ea& to re%ain position8 +&&itional recor&in% elements on t*e*ea& are locate& at precise &istances rom t*e ser'o sensors= allowin% accurate writin%an& rea&in% o &ata tracks8

Le'era%in% t*e track-ollowin% ser'o met*o& &eploye& in t*e !a%star 79= in

6o'ember 199>= I.!= "ewlett Packar&= an& Sea%ate announce& a new linear tape ormator mi&-ran%e tape pro&uct customers calle& L,;8 ,o%et*er= t*ese companies &eine& an

a%%ressi'e tec*nolo%y roa& map or L,; an& ma&e it a'ailable to any &ri'e or me&ia


22/27

manuacturer t*rou%* a licensin% process= supportin% t*e belie t*at multiple competin%

manuacturers will assure lon%-term stability= better pro&uct a'ailability= an& more

competiti'e pricin%8 L,;-compliant &ri'es are e3pecte& rom I.!= ?uQitsu= "ewlettPackar&= an& Sea%ate= an& i'e me&ia manuacturers *a'e purc*ase& licenses to make t*e

L,;-ormat me&ia8

Concurrently= Muantum Corporation *as &esi%nate& SDL,= base& on its DL, tec*nolo%y=

as t*e ormat o c*oice or its ne3t si%niicant tape pro&uct8 ?urt*er= Muantum *asin&icate& t*at t*ey will implement a new optical ser'o tec*niFue calle& Laser ui&e&

!a%netic Recor&in% /L!R0= w*ic* pro'i&es t*e ser'o wit* position inormation by

s*inin% a laser on a relecti'e strip manuacture& on t*e back o t*e tape8 Proponents oL!R claim t*at t*is tec*niFue eliminates t*e cost an& incon'enience o writin% ser'o

reerence tracks on t*e me&ia an& allows more tape surace area to be a'ailable or &ata

stora%e8

+lt*ou%* t*e L!R met*o& may sa'e incon'enience= me&ia manuacturers can easily

eliminate a&&itional costly steps in t*e L,; met*o& by writin% t*e ser'o tracks as t*eyloa& t*e tape into t*eir cartri&%es8 (*ile ser'o reerence tracks occupy se'en percent o

t*e tape area= t*e loss o space is amply compensate& by t*e &ata inte%rity t*ey pro'i&e8+&&itionally= wit* planne& impro'ements in track spacin% an& bit &ensity alon% a track=

t*e L,; ormat will allow uture &ri'es to oer capacities up to .8

"owe'er= t*e most crucial &ierence between tape ser'o systems is t*e issue o

reliability8 $sin% t*e L!R optical trackin% met*o& is like &ri'in% a car on a roa&wit*out 'isible lanes w*ile watc*in% a me&ian o'er 18 miles away8 ,*is calculation is

&eri'e& by scalin% up t*e track wi&t*= assume& to be appro3imately 2>Hmicrom= to a

stan&ar& lane wi&t* o 14 eet8 ,*e conseFuences o a *ea& mo'in% o track un&er t*ese

circumstances can be &isastrous--in less t*an a secon&= 1!. o &ata coul& beobliterate&8 ,*e track-ollowin% ser'o met*o& use& on L,;-compliant &ri'es oers a

more robust approac* by locatin% reerence tracks close to t*e recor&e& &ata rat*er t*anon t*e ot*er si&e o t*e me&ia8

D0D Features3

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Di%ital an& analo%ue copy protection or D


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pt#cal $ecord#n! +&aracter#st#cs *J Re?or!ing pe MgnetiztionRe>er-lJ Re?or!ing Met*o! Spottemperture ele>tion nerCurie point

J Re!ing Met*o! /err Angle!i55erentitionJ Pro!u?t- M (Mgneto0opti?l)

Fi#ure 5b6 ,ptical Recordin# $%aracteristics3 !a#neto-optical recordin#Re?or!ing pe3 StteC*nge#3 PolmerDe?*r?teri-ti? ?*ngeRe?or!ing Met*o!3 Pittempertureele>tion#3 Pittempertureele>tionRe!ing Met*o!3 Re5le?ti>it!i55erentition#3 Re5le?ti>it!i55erentitionPro!u?t-3 PC (p*-e?*nge)DKD0RAM#3 CD0R


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DKD0R

#pt#cal $ecord#n! +&aracter#st#cs 3 6 7Fi#ure 5c6 ,ptical Recordin# $%aracteristics3 Polymer Dye and P%ase $%an#e

29

Data Recovery

In tec*nolo%ies 1= 7 an& 4= t*e relecti'ity &ierence between recor&e& an& unrecor&e&

areas is &etecte& an& use& to %enerate an electronic si%nal8

In CD-+u&io= CD-R;!= D> by @o*n Aerr8 In !; recor&in%= t*is small rotation is use& to %enerate

t*e rea& si%nal8

Factors determinin# ,ptical Recordin# Density

,*e &iameter o t*e ocuse& laser beam is t*e &eterminant o areal &ensity e3cept in t*e

case o inQection-mol&e& me&ia8 ,*e &iraction-limit


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information about scsi

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