scsi drives chapter 13 release 22/10/2010powered by dj

SCSI Drives

Chapter 13

Release 22/10/2010 powered by dj

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Objectives - I

List the advantages of SCSIList the different SCSI interfacesIdentify the SCSI variationsList the different types of SCSI signalsUse the SCSI ID


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Objectives - II

Work with SCSI connectorsUse the different SCSI cablesWork with SCSI drivesInstall SCSI drivesTroubleshoot the SCSI drive


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Advantages of SCSI - I

Data transmission speeds reach about 320 MB per second between the system and the device

Allows to attach 15 devices to a single SCSI port

SCSI controller boosts the signals and enables the devices to be connected at a distance of about 25 meters from the system


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Advantages of SCSI - II

Reduces the processing load on the microprocessor, as they have a micro-controller built into the device

Communication problems between the system and SCSI device are reduced as the ends of the SCSI have terminators


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Types of SCSI Interface and show P-3 of CBT

SCSI – 1 - Uses an 8-bit parallel bus to transfer data at a maximum speed of 5 MB per second. Can connect up to 8 devices with a cable length of 6 meters and uses passive terminators

SCSI – 2 - Uses a 16-bit bus to transfer data at a maximum speed of 20 MB per second. Can connect up to 8 devices and cable length of 3 meters. Uses 50 pin connector, command queuing feature and active terminator

SCSI – 3 - Uses a 16-bit bus to transfer data at a maximum speed of 40 MB per second. Can connect up to 16 devices and cable length is 3 meter. Uses active terminators


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Question for GD Time Limit – 2 Mins

What are the different types of SCSI?


Sl. Types of SCSI

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SCSI Variations - I

Narrow SCSI – Transmits data over an 8-bit bus. Uses 50 pin connector cable known as A cable

Wide SCSI – Transmits data over a 16-bit bus. Uses 68 pin connector cable known as P cable

Fast SCSI – Transfers the data at the speed of 10 MB per second using the narrow SCSI

Wide Ultra – Transmits data at a speed of 20 MB per second for the narrow SCSI


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SCSI Variations - II

iSCSI - (Internet SCSI) is a TCP/IP based protocol. It is used to establish and manage the connections between IP based storage devices, hosts and clients. iSCSI has almost same command set as basic SCSI which helps in preserving the basic SCSI standard.

Serial SCSI - The Serial SCSI performs the data transfer through serial communication. SSA (Serial Storage Architecture), Fibre channel, FireWire and SAS (Serial Attached SCSI) are the four versions of Serial SCSI.


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What is the difference between narrow and wide SCSI?


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SCSI Variations - III

SCSI Drive speeds – Available at speeds of 10,000 rpm to 15,000 rpm

Universal hard drive – Easy to upgrade the server hard drives and supports S.M.A.R.T feature

Serial Attached SCSI (SAS) – Allows much higher speed data transfer (6 Gb/s) than previously available and is backward compatible with SATA. Uses SCSI commands for interacting with SAS devices


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What are the different SCSI variations?


Sl. SCSI Variations

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Types of SCSI Bus Signaling - I

Single-Ended (SE) – Transmits a positive voltage through a signal line to the receiver. Maximum cable length is 6 meter

High-Voltage Differential (HVD) – Reduces problems of bouncing signals, signal interference problems, noise and crosstalk. Enables cable length up to 25 meters. It is very costly


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What is the difference between SE and HVD bus signaling?


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Types of SCSI Signaling - II

Low-Voltage Differential (LVD) – Signals are transmitted using the difference in the voltage between the two wires. SCSI device adapter has a small transceiver built into it which boosts signal. Uses 3.3 voltage to represent logical 1 or 0

Low-Voltage Differential/ Single- Ended Multi-mode (LVD/SE) – Compatible with LVD and SE signaling. However if there is a device that uses SE signaling on SCSI bus, then this will be set to use SE signaling


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What are different SCSI bus signaling?


Sl. SCSI Signaling

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Working with SCSI Identification (ID) - I

Jumper Block/ DIP Switch Settings – SCSI identification is set using software available with SCSI device, using the jumpers or switches on the SCSI device

Resolving Id Conflicts – SCSI identification specifies the priority in which the device has access to the bus. Host SCSI controller on the system is generally given the highest SCSI priority 7 to ensure that it gets first access to system resources. SCSI hard drives are factory set to have ID 0


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Working with SCSI Identification (ID) -II


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Practical

Perform the activity mentioned in Lab no. 1 in the text book:

• To set the SCSI ID using switches.


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Working with SCSI Connectors

Internal Connectors – Located on SCSI devices such as hard disks and CD drives that are installed inside the system case

External Connectors – Located on the SCSI adapters and the SCSI devices such as printers, scanners and external tape drives


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Which type of connector is used for Ultra3 320 SCSI drive?


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Using SCSI Cables

Type• Internal SCSI Cable – Flat ribbon cable

• External SCSI Cables – Thick round cable


Internal SCSI Cable External SCSI

Cable

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Practical Activity Time Limit – 4 Mins

Show different internal and external SCSI cables to students


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Termination Requirement - I

SCSI devices use passive and active terminators. Some devices also have the passive terminator

built into them or have jumpers to activate the terminator.

SCSI bus requires two terminators one at either end of the SCSI bus.

However, you must not attach a terminator directly on the host controller.


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Termination Requirement - II

Terminators are powered from the term power line on the SCSI bus.

Term power can come from any device on the bus, and is provided by either the host, a drive on the bus, the backplane, or any combination thereof.

Term power is provided through a diode and fuse and allows for a term power range of 4.0 to 5.25 volts


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Types of Terminators - I

Internal - Some SCSI drives (pre-LVD) had passive terminators installed in the drive, and could be enabled/disabled by setting a jumper or inserted/removed from a socket. Drives with LVD interface do not have internal termination.

External - In-line (also called ‘feed-through’) terminators connect in series with a SCSI device. Close-ended terminators plug into a bus connector or may be crimped on the cable.


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Types of Terminators - II

Passive Terminator – Use a resistor to terminate the SCSI signals and if the distance between the last device on the SCSI chain and the SCSI controller is less than 1 meter

Active Terminator – Use a resistor and a voltage regulator and if the distance between the last device on the SCSI chain and the SCSI controller is more than 1 meter


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Passive and Active Terminator


ActivePassive

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What is termination? List the different types of terminators.


Sl. Types of Terminator

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RAID - I

Redundant Array of Inexpensive Disks (RAID) is a collection of hard disks that appear to the system as a single disk• RAID Level 0 - Data is broken into blocks • RAID Level 1 – total disk space available is half

of total capacity of disks• RAID Level 4 - Data are broken up into blocks of

small size and distributed on various disks and parity blocks are stored in a dedicated disk.


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What is RAID and what is it’s advantages?


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RAID - 5

Frequently used method to RAID hard disks. Data as well as the parity information is stored on

multiple disks. If one drive fails, the failed disk can be recreated

after it is replaced. It is preferable to use hard disks of same storage

capacity to implement RAID Level 5. Available disk space is the sum of the size of all

disks minus the size of one disk.


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RAID - 5

RAID Level 5 requires a minimum of 3 disks to be implemented.

If two hard drives crash simultaneously then data cannot be retrieved.


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What is RAID5 and why it’s mostly used in organizations?


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RAID - II

• RAID Level 6 - It is similar to RAID 5 but uses an additional parity block.

• It employs two parity blocks for additional data protection.

• If two hard drives crash simultaneously, data can still be retrieved.

• Requires a minimum of 4 disks to be implemented.


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RAID - III

RAID 0+1 - It implements both striping and mirroring data among disks. Two RAID 0 stripes are created and a RAID 1 mirror is created over those two disks. RAID level 0 + 1 requires a minimum of 4 drives to be implemented.

RAID 10 - This uses disk mirroring and stripping without the use of parity which results in better data security and performance.


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RAID - IV

• RAID 50 – RAID level 50 is a combination of RAID level 5 and RAID level 0.

• Combines striping of RAID 0 with distributed parity of RAID 5.

• Requires at least six drives. • It is implementing across two RAID 5

arrays. • It divides the data into smaller blocks and

stripes the blocks into each RAID 5 raid set.


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Group Activity Time Limit – 5 Mins

Draw a window pane on different RAID levels.


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Hot Swap Drives


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Installing SCSI Drives and show from CBT - I

Installing the Host Adapter – Given the highest priority over SCSI bus so that it can serve other devices properly

Installing the Internal SCSI Device – Connects to the host adapter bus using the SCSI cable

Terminate the ends of SCSI cable. LVD drives do not have any provision for onboard termination; therefore, termination for LVD drives must come from another device or from an external terminator


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Installing SCSI Drives and show from CBT - II

Configure Terminator Power - Active terminators must receive power from some source.

The default configuration results in the drive not supplying termination power to the bus.

Usually, the host adapter provides term power. Check the user's manual for your host adapter.


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Practical

Perform the activity mentioned in Lab no. 2 in the text book:

• To install a SCSI host adapter and an internal SCSI device.

• Click on the image to run the video.


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SCSI HD Detect Video


Click on the image to run the video.

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Troubleshooting - I

Problem with the SCSI Daisy-Chain –

o In a daisy chain any problem with any one device may cause all the devices to malfunction

o Check that the power supply is switched on for all the devices

o Check that the cables in the daisy-chain are properly connected and not loose

o Check that both ends of the SCSI daisy-chain are terminatedo Check that the SCSI ID is not repeated for two or more

deviceso Disconnect all the devices and reconnect them one by oneo Reinstall the device drivers


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Troubleshooting - II

The Connected Device is not Functioning Properly -

o Check if the devices are connected properlyo Ensure that the terminators are secured properly

at the ends of the SCSI daisy-chaino Change the SCSI ID of the deviceo Reinstall the device driver


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Summary I Small Computer Systems Interface (SCSI) enables

you to attach peripherals to the system SCSI consists of controller, cables and the device Advantages of SCSI:

• Faster transfer of data

• Attach multiple devices

• Devices can be placed at a distance from the system

• Reduces load on microprocessor

• Reduces reflection of data signals


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Summary II SCSI standards specify the features of SCSI

devices SCSI bus signaling specifies the method used by

the SCSI devices to communicate with each other Different SCSI signaling methods:

• Single-Ended

• Low-Voltage Differential

• High Voltage Differential

• Low-Voltage Differential / Single-Ended Multi-mode


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Summary III

The SCSI ID specifies the priority of the SCSI device on the SCSI bus

SCSI connectors enable you to affix the SCSI cable to the SCSI adapter or the SCSI device

The SCSI terminator is used to terminate the SCSI daisy-chain


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Summary IVActive terminators have a resistor and also a

voltage regulatorRAID is a collection of hard disks that

appear to the system as a single disk Hot swap drives enable you to connect and

disconnect drives to the system without shutting down or restarting the system

Installing SCSI host adapter, internal and external SCSI drives


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Explorative Work

Refer to Internet, reference books or magazine to get the information.

Do not copy the information provided in this text book. Consult your faculty for further guidance.


SCSI Drive

Sl. Make SCSI/SASType of Interface

Speed (rpm) Capacity DTR Connector

Hot swappable (Y/N)

Year of Release

1

2

3

4

5

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Mind Map

Draw a mind map to summarize this chapter


scsi drives chapter 13 release 22/10/2010powered by dj

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