Download - Time Finder

Copyright © 2004 EMC Corporation. All Rights Reserved.

TimeFinder, 1

EMC Global Education© 2004 EMC Corporation. All rights reserved.

Symmetrix Business ContinuityTimeFinder

The purpose of this module is to give students hands-on experience with TimeFinder in an Open Systems environment. TimeFinder allows dynamic full image copies of data with Business Continuance Volumes (BCV), point-in-time copies through Clones, and logical point-in-time views of production information though Snapshots.


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Objectives

At the completion of this module, you will be able to:Describe EMC TimeFinder functionality and it’s usesUse SYMCLI to perform TimeFinder operationsDescribe TimeFinder Host considerations and configurationsExecute TimeFinder Clone operationsExecute EMC Snap operations and check status of save devices


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Facility that allows an administrator to create, split, and use a mirror copy of a Symmetrix volume Additional mirror within same SymmetrixMay be used with SRDF source or target volumes Maintain Disaster Recovery capability while enhancing operational environmentImplemented using Business Continuance Volumes (BCV)Snapshots use only a fraction of the original source dataClones require equal amount of disk space

TimeFinder

Sales

Billing

BackupsWeb contentrefresh

Data warehousingApplication testing

Local recovery1-hour recovery point objective

Standardvolume

BCV

Standardvolume

Clone

Snapshot

Snapshot

Meeting Local Replication Service Levels

The EMC TimeFinder family of products allows companies to make more effective use of their most valuable resource information by enabling parallel information access. Instead of traditional sequential information access that force applications to queue for information access, TimeFinder allows multiple business processes to have concurrent, parallel access to information.TimeFinder allows dynamic, full image copies of data with Business Continuance Volumes (BCV), point-in-time copies through Clones, and logical point-in-time views of production information though Snapshots.


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EMC TimeFinder Business Continuance Volume (BCV)Uses Business Continuance Volume (BCV) to create an additional mirror image of a standard device– Can be dynamically and non-

disruptively established and synchronized

– Can be split instantly to create “point-in-time” copy

“Point-in-time” copy can address workload compression and maintain continuous business operation– Data Protection - Standby data

for fast recovery– Decision support – Backup

1. “Establish” BCV 2. “Query” BCV status until completely synchronized3. Quiesce application and flush buffers4. “Split” BCV5. Restart applications6. Execute BC operations using BCV

BCV Split

BCV Established

STDSTDSTDSTD

BCVBCVBCVBCV

TimeFinder allows companies to make more effective use of their most valuable resources by enabling parallel information access as opposed to traditional sequential information access, thus eliminating the need to do things like quiesce an application for backups.BCV and standard devices should be configured on opposing Front End and Back End Directors for redundant paths.TimeFinder Business Continuance is possible due to Business Continuance Volume (BCV) devices. These BCV devices are standard Symmetrix devices that are specially configured to be dynamic mirrors. Each BCV device has its own host address and is configured as a stand-alone device.EMC ControlCenter provides an interface to control the use of BCV devices that already exist in the Symmetrix configuration. Configuring Symmetrix units as BCV devices is done by the Customer Service Engineer during installation, or by the customer with Symmetrix Manager ECC software.


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TimeFinder Basic Operations

Establish BCV pairs– Synchronize the standard volume to the BCV volume– Options

• Full or Incremental (default)l Establish• -exact• -opt

Split BCV pairs– Terminate mirror relationship between BCV and

standard volumes – Options

• Differential Split (default) • Reverse Split• Instant Split (default) • Consistent Split

Restore BCV pairs– Synchronize contents of BCV volume to the standard

volume– Options

• Full or Incremental (default) Restore

Verify all BCV device– Provide current status of BCV/standard volume pairs

BCVBCV

BCVBCV

BCVBCV

StandardStandardVolumeVolume



TimeFinder allows the user to create several host-based business continuity operations and control these operations through host commands. The user can establish a BCV, then split it to make the BCV available to a host/server. After completing the business continuity processes on the BCV device, the user can re-establish the BCV pair. Typical BCV operations include establish, split, re-establish, restore, incrementally restore, and verify.


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TimeFinder Extended Operations

Protected BCV Restore -Restore a BCV to a STD but do not propagate STD writes to the BCV– Used to retain original BCV data after

the restore process

BCVBCVStandardStandardVolumeVolume

Reverse Split - By specifying a reverse split, data can be moved (full or differential) from the M2 mirror of the BCV to it’s M1 mirror

Protected BCV Establish -Moves all mirrors of locally mirrored BCV so all mirrors are instantly synchronized

BCVBCVM1M1

STDSTDM2M2

STDSTDM1M1

BCVBCVM2M2

BCVBCVM1M1

STDSTDM2M2

STDSTDM1M1

BCVBCVM2M2

The extended BCV operations include protect establish, reverse split, and protected restore. These operations add flexibility to TimeFinder configurations and allow for added protection of gold BCV copies.


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Incremental establish

or

Incremental restore

StandardStandardvolumevolume

BCVBCV 4:00 a.m.

2:00 a.m.

4:00 a.m.

6:00 a.m.

StandardStandardvolumevolume

EstablishSplit

EstablishSplit

BCVBCV

BCVBCV

BCVBCV

Multi-BCVsStandard device keeps track of changes to multiple BCVs one after the otherIncremental establish or restore now possible with up to eight BCVs

By default, TimeFinder can “remember” up to eight BCVs. This means that different BCVs can be established and then split from a standard volume at different times of the day. It used to be that the Symmetrix did not keep track tables for the previous BCVs; the track table was only for the last, most recent BCV. Thus, a BCV that was split at 3:00 a.m. could not be re-established if another BCV had been established and split at 4:00 a.m. The 3:00 a.m. BCV would have to be established (full volume copy) again.With the Multi-BCV function, up to eight BCVs will be remembered by the Symmetrix. In other words, a BCV that was split at 4:00 a.m. can be re-established even though another BCV was established and split at 5:00 a.m. In this way, a user can split and incrementally re-establish volumes throughout the day or night and still keep re-establish times to a minimum.Incremental information can be retained between a STD device and multiple BCV devices, provided the BCV devices have not been paired with different STD devices.


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1) Identify two Regular Volumes and four BCVs for use2) Create two SYMCLI Device Groups of type Regular - AMdg and PMdg3) Add the two Regular Volumes to AMdg. Associate the first two BCVs in

set one, with AMdg4) Associate the next two BCVs in set two with PMdg (as yet does not

have any Regular Volumes added to it) 5) Create a Volume Group, Logical Volume, File System, using the

Regular Volumes. Add some files to the filesystem6) Full establish AMdg, verify synchronization, freeze I/O then split AMdg 7) Move the Regular Volumes to PMdg, full establish, verify

synchronization8) Add/delete some files from the filesystem. Split PMdg, Move Regular

Volumes to AMdg, stop I/O, restore to recover “lost” files

Multi-BCV Example

By default, relationships of one STD device with up to eight BCV devices can be maintained.Maximum number of BCV devices that can be paired with the same STD device can be increased up to sixteen: SYMCLI_MAX_BCV_PAIRS variable.


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Each BCV will occupy a mirror position - locally protected R1 Volumes cannot have two BCVs established with them concurrentlyEstablish two BCVs with the same standard simultaneously or one after the otherThe BCVs can be split individually or simultaneouslyConcurrent restores, either simultaneously or successively, is not allowed

Concurrent BCVs

StandardStandardBCV1BCV1

BCV2BCV2

m1 m2 m3 m4

Concurrent BCVs is a TimeFinder feature that allows two BCVs to be simultaneously attached to a standard volume. The BCV pair can be split, providing customers with two copies of the customer’s data. Each BCV can be mounted online and made available for processing.


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Consistent Split - PowerPath and ECAPowerPath split

PowerPath holds I/O during split- Read and write I/O

Executed from host doing I/OAffects only one hostDoes not require independent access to a gatekeeper

symmir -instant –ppathsymmir -instant -rdb

Symmetrix holds I/O during split- Write I/O (subsequent reads after first write)

Executed by any Symmetrix-attached host Multiple host supportRequires independent access to a gatekeeper

Enginuity Consistent Assistsplit symmir –consistent

HostHost

STDSTD BCVBCVBCVBCVSTDSTD

Performs an Instant Split across a group of devices using a single Consistent Split command, thus all the BCVs in the group are consistent point-in-time copies. Used to create a consistent point-in-time copy of an entire system, an entire database, or any associated set of volumes. Can create consistent splits on remote BCVs through SRDF.PowerPath-based consistent split executed by the host doing the I/O:

• -rdb option• -ppath option

I/O is held at the host before the split. ECA-based consistent split can be executed:

• By the host doing the I/O as long as there is a dedicated path for a gatekeeper to perform the control• By a control host (no database) in an environment where there are distributed and/or related databases• -cons option

I/O held at the Symmetrix until the instant split operation is completed:• Approximately 3 seconds.

Available on Solaris, HP-UX, AIX, Tru64, and W2K platforms Since I/O is held at the Symmetrix, ECA can be used to perform consistent splits on BCV pairs across multiple, heterogeneous hosts.


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TimeFinder Host ConsiderationsWhile established, BCV is a mirror to the STD device and is not accessible by the hostAll access to a BCV must be stopped before it is established – Stop application, unmount filesystem, and

deactivate volume groupAny attempt to access the BCV device while it is established will result in an I/O error– inq command will hang and timeout– Activating a volume group or mounting a

filesystem that resides on a BVC while the BCV is established will result in an I/O error

If the host is re-booted or reconfigured while the BCV is established, the BCV will not be detected and may cause it to be removed from the host device configuration

Before a BCV is established to a standard device, it can be accessed by a host as a separate and independent device

NRRW

M1 BCVM2M1 M2 BCV

TimeFinder provides host-transparent, "splittable" mirrors that can be used in a variety of ways to enhance application availability and reliability. On the BCV host side, TimeFinder operations are not transparent. When the BCV is established with the standard volume, it becomes unavailable to the BCV host system. Any attempt to access the BCV will fail.If the host is re-booted or reconfigured while the BCV is established, the BCV may not be detected and may cause it to be removed from the host device configuration. AIX addresses established BCV issues by automatically configuring the BCV as a “Defined” device in the AIX ODM. When a reboot occurs, the BCV is not automatically configured. BCV devices that are not established can be configured during reboot with the EMC command mkbcv. BCV devices that are established can be made available with mkbcv after they have been split.


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TimeFinder Host Considerations

When a BCV is split, it can be used by the same host or by a different hostThere are LVM issues when both BCV and Standard device are accessed from same host– UNIX Systems – Duplicate Physical Volume Ids and Volume Group Ids– Windows 2000 – Duplication of disk signatures and Volume configuration information

RWRW

M1 BCVM2

RWRW

M1 BCVM2

A split BCV is an identical copy of the volume it was dynamically mirrored to. When accessing the BCV on the same host as it’s mirror duplicate, volume information must be changed.


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TimeFinder Multiple Host Environment

When a Standard volume and a BCV is split, a different host can easily access the volume group by “importing” the volume groupThere is no conflict with PVIDs and VGDA information because each host only accesses one copy of the dataThere is also a performance benefit when BC applications use a copy of the data on a non-production host

RWRW

M1 BCVM2

PVIDVGDA

standardPVIDVGDA

BCV

Identical Information

When accessing a BCV on a second host, there are no duplicate Ids to consider. The device can simply be brought online using standard host controls.


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Host A Host B

1. symmir establish 2. Quiese

application

3. Umount filesystem

4. Deactivate VG 5. symmir split 6. Reactivate VG Import VG 7. Remount File

System Mount File System

8. Restart application

Repurpose Data

RWRW

M1 BCVM2

PVIDVGDA

standardPVIDVGDA

BCV

TimeFinder Multiple Host Environment

This slide shows the basic steps for accessing a BCV on a secondary host in a TimeFinder environment. It performs a “clean” split operation which would require no form of recovery from the application when restarted at the secondary host. It does not take into account the use of consistent split that would perform a freeze/thaw on the application to allow for a consistent point-in-time copy of the data at the secondary host, but could require a level of recovery.


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TimeFinder Host Considerations – Same Host

When both the BCV and the standard volume are accessed by the same host, there is a conflict Both the Standard and BCV volume

have identical PVIDs and VGDA information

Host expects the PVID and VGDA to be unique

Additional steps must be taken before the host can use both the BCV and the standard device

RWRW

M1 BCVM2

PVIDVGDA

standardPVIDVGDA

BCV

Identical Information

Accessing a BCV on the same host as the original production data requires addressing duplicate disk identifiers in order to access the device. Each operating system has unique methods for addressing the duplicate identifiers.


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recreatevg Utility– The recreatevg command is run on all the BCVs of a given Volume Group.

The command resolves the duplicate PVID issues and creates an identical Volume Group as that on the Standard volumes. New mount points for the file systems on the BCV Volume Group is created as well.

#recreatevg -y backup_vg -Y backup_ -L /backup hdisk11 hdisk12

#lsvg -l backup_vg

backup_vg:

LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT

backup_stdlv jfs 50 50 1 closed/syncd /backup/stdfs

backup_loglv00 jfslog 1 1 1 closed/syncd N/A

#mount /backup/stdfs

#ls /backup/stdfs

lost+found tf.dat

Accessing BCV on same HostIBM AIX

Changing the PVID and VGIDs enables you to import the contents of the mirror volumes using a unique volume group name (that is, a different volume group name from that of the standard volumes). Once the PVIDs and VGIDs have been changed, the mirror volumes can be imported into a new volume group using the importvg command.


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vgchgid command to change the Volume Group ID on one or more Physical Volumes that make up a Volume Group.– Eliminating the problem of duplicate VGIDs

when a BCV is split, and both the Volume Group on the Standard and the BCV Volumes are available to the same host

– Implemented specifically for EMC Symmetrix and TimeFinder environments

vgchgid /dev/rdsk/c2t5d101

– Specify all Physical Volumes in the BCV Volume Group.

• All Physical Volumes must have BCV attribute

• All Physical Volumes must belong to the same Volume Group

PVIDVGRA (VGID)

standardPVID

VGRA (VGID)

BCV

PVIDVGRA (VGID)

standardPVID

VGRA (New VGID)

BCV

After a BCV is split, both the standard and the BCV volumes will have identical information; including the VGID

vgchgid makes the VGID unique

Accessing BCV on same Host

HP UX

Changing the VGIDs enables you to import the contents of the mirror volumes using a unique volume group name (that is, a different volume group name from that of the standard volumes). Once the VGIDs have been changed, the mirror volumes can be imported into a new volume group using the vgimport command.


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Generate a map file for the standard volume group– vxprint -m -g <std volume group name> <mapfile.txt>

Deport the standard volume groupCreate a volume group on the BCVs– vxdg init <bcv group name> <1st BCV disk>– vxdg -g <bcv group name> adddisk < 2nd BCV disk>

• Add all the disks in the order in which they appear in the standard volume groupEdit the map file, removing all DG and DM entries and changing name of the standard disk (the SD entry) to the name of its associated BCVCreate all of the necessary plexes and volumes for the BCV volume group– vxmake -g <bcv group name> < mapfile.txt>

• This creates a volume layout that is identical to the one on the standard disksForce start all of the volumes inside the BCV volume group– vxvol -g <bcv group name> -f start <volume name>

Mount the file system on the desired directory

Accessing BCV on same Host SUN Veritas

This slide shows the steps to make the BCV available to the same host in a TimeFinder environment. It should be seen as a proof of concept and not as a proven methodology.


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With Basic Disks, it is possible to mount the BCV and Standard devices on the same host via signature manipulation with Symmetrix Integration UtilitiesWith Dynamic Disks, it is not possible to mount a BCV on the same host as the StandardSuggested Best Practices with Dynamic Disks– Create Dynamic Disk Groups that correspond one-to-one with SYMCLI device groups– Do not mix STD and BCV devices in the same Dynamic Disk Group– Do not have Symmetrix and non-Symmetrix disk in the same Dynamic Disk Group– Do not mix R1 and R2 devices in the same Dynamic Disk Group– Do not add gatekeeper-devices to any Dynamic Disk Group

Accessing BCV on same HostWindows 2000

Accessing the BCV on the same host in a Windows 2000 environment requires a Basic Disk configuration. It is not possible to mount a Dynamic Disk BCV on the same host as the Standard Volume.


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TimeFinder Restore

During a symmir restore operation, data on the standard is replaced with data from the BCV volumePrimary host still has full read/write access to the standard volumeIf an application is using the standard volume during a restore, the results would be unpredictableApplications should be stopped, file systems unmounted, and volume groups deactivated when a restore is initiated

NRRW

M1 BCVM2

Remember that “restore” is a recovery operation. So applications should be stopped, files systems unmounted, and VG deactivated before you issue the restore command.


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1. Perform normal shutdown of database2. Split BCV for all devices in data set3. Restart, mount, and open database on

Standard Devices

4. Adjust control files to reflect file/device names

5. Start second database instance or begin full backup of all files/devices from BCV Devices

BCV Devices

Initialization File

Control File

Redo Log

Table Space

Standard Devices

Initialization File

Control File

Redo Log

Table Space

Offline Database Backups with TimeFinder

A cold backup can be taken only when the database is offline (that is, after it has been shut down).A few preliminary steps must be performed before conducting a cold backup. First, you split the BCV devices for all currently established data files, online redo log files, and control files. Then, while the primary database is up and running, you use a second database to perform the backup.


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1. alter tablespace ts_name begin backup

2. Split BCV for Table space files/devices

3. alter tablespace ts_name end backup4. Archive current REDO log file and

control files

5. Recreate control files to reflect file/device names

6. Start second database instance startup nomount

7. Recover table spaces by applying archive logs

8. Open database for DSS/BR

BCV Devices

Initialization File

Control File

Redo Log

Table Space

Standard Devices

Initialization File

Control File

Redo Log

Table Space

On-line Database Backups with TimeFinder

The actual procedure would be some thing like this:• Issue a DB checkpoint – alter system checkpoint; get the highest archivelog file number prior to the split – ls

/archive_destination/*.dbf• DBA issues alter tablespace ts_name begin backup; typically, each TS will be placed in a hot backup mode, its

*.dbf file(s) copied to a destination, removed from hot backup mode before proceeding with the next TS. In a TF split environment, this is not done. ALL TS are placed in HB mode at once. This will increase the redo activity, but this is how it is done! However, an “instant” split operation will minimize the time for which the TS are in a HB mode. To get a list of TS, use select * from v$tablespace; to list the files in HB mode use select * from v$backup. Alternatively, one can use symioctl –type Oracle begin backup. This will place ALL TS in HB mode.

• Optionally alter database suspend; or symioctl –type Oracle freeze either of these will freeze IO to the DB. This again will minimize the redo activity – however, transactions will not proceed.

• symmir –instant split – split all volumes other than the log and controlfile volumes. On-line redo logs and controlfiles need not be BCVd.

• Issue alter database resume; or symioctl –type Oracle thaw (if suspend/freeze has been used), and alter tablespace ts_name end backup; or symioctl –type Oracle end backup

• Archive the current log file – alter system archive log current; (split the log and controlfile volumes if they are also BCV’ed)

• Create a backup controlfile – alter database backup controlfile to trace• Start the BCV DB – startup restrict nomount; recover DB – recover database; shutdown normal; startup


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TimeFinder ClonesA TimeFinder clone is an instant point-in-time copy of a Symmetrix standard device or TimeFinder BCV:

– Copying can be immediate or deferred (copy on access)

– Copying is controlled by copy sessions

– Copy sessions are maintained on the Symmetrix unit

– Copy sessions are created, activated, queried, listed, and terminated using the symclonecommand

– Data can be copied from a single source device to as many as sixteen target devices, with automatic background copying of up to four target devices simultaneously

Source

Target

Host

HostCopy

Clones are full volume copies of a source device in open systems which are pointer-based. When creating a clone image, it is not necessary to first perform a full establish operation as you would with traditional TimeFinder BCVs. Upon activation of the cloned image, it is fully read/write enabled; data is copied in the background as it is accessed. The Symmetrix array is currently limited to sixteen sessions per source device, which can be used for TimeFinder Mirror, Clone or Snap operations. This limits the number of available clone copies that can be created. A total of sixteen concurrent CopyOnAccess copy sessions can be created from a standard device (sessions created without using the -copy option).


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TimeFinder Clones: Creating a Copy SessionThe symclone create command:

– Makes the target not ready (NR) to its host– Creates a copy session– Sets up the track protection bitmap to provide user access

to data on the target as soon as the clone pair is activated– Puts a hold on the target to prevent other control

operations (for example, TimeFinder operations) or a copy over previously copied data

– The -copy option will make an immediate copy of the entire source to the target. Copying begins upon issuing the symclone activate command

The syntax is:symclone –g clonegrp create DEV001 sym ld DEV002

When you issue the symclone create command, the target device is made not ready to its host. This operation then sets up the track protection bitmap to provide user access to cloned data as soon as the clone pair is activated.The minimum enginuity levels required for symclone usage is:

5568.56.225669.45.245670.23.25


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TimeFinder Clones: Activating a Copy SessionThe symclone activate command:

– Places the target in the Read/Write (RW) state– Initiates copying if the -copy option has been specified

in the symclone create command– Omitting the -copy option in the symclone create

command defers data copying until either tracks on the source are written to or tracks on the target are read or written to

A user on the target’s host can access data on thetarget, even while copying is in progress.The syntax is:

symclone –g clonegrp activate DEV001 sym ld DEV002

When you issue the symclone activate command, the target is made ready again. A user on the target’s host can then access data on the target immediately:•If the target’s host attempts to read from or write to the target device tracks that have not been copied yet, the system finds those tracks on the source device and copies them immediately to the target, then services the I/O request.•If the source’s host attempts to write to the source device tracks that are not copied yet, the system finds those tracks on the source and copies them immediately to the target, before those writes to the source can occur on the source.


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TimeFinder Clones: Terminating a Copy SessionThe symclone terminate command:

– Stops a copy session– Removes any hold on the target– Deletes copy session information from the Symmetrix unit

Normal termination is possible whenever a copy pair is in the Created, Copied, or CopyOnAccess state

The syntax is:symclone –g clonegrp terminate DEV001 sym ld DEV002

When terminating a pair relationship, no conflicts exist if the pair is in the Created state or in the Copied state. However, stopping a copy session for a pair whose state is CopyOnAccess or CopyOnWrite may end the session prematurely if an application has not finished accessing data or if writes to the source device are ongoing. Terminating a pair is not allowed when the pair state is CopyInProg.


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Restoring from a TimeFinder Clone

Restoring from a Clone it is not a restore but a new CloneSteps would be:– Create a clone with a –copy option– After the copy is complete, terminate the clone session– Start a fresh cloning session using old target as new source

Clones are full volume copies of a source device in open systems which are pointer-based. When restoring from a clone image, it is a matter of reversing the direction of the source and clone. If the clone has not been created with the –copy option, the integrity of the target may be in question. This could compromise the integrity when making the old target the new source since there is no way to verify the data on the clone is a complete copy.


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Clone PerformanceNo impact to reads on source from existence of clone volume (With no workload on target)

– Workload on target could cause disk contention with source until fully copied

Write response time to protected tracks (first write to track) are higher than a normal cached write

– From < 1ms to > 10ms– Could be slightly faster if protected track is in cache– Small sequential writes less effected than large or random

writes as track is unprotected on first accessFirst reads from target are slower than from STD or from a split BCV because of the copy on read needed for clone target device

Clone performance has no impact to reads on the source as long as there is no workload on the target. Workload could cause disk contention with the source until the clone is fully copied.


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EMC Snap for Symmetrix DMXSnapshots create logical point-in-time images of a source volumeRequires only a fraction of the source volume’s capacity Multiple snapshots can be created from a source volume and are available immediately Snapshots support both read-only and read / write processingComplements TimeFinder and provides unmatched replication flexibility

Save Area

Production view

Snapshot view

Production volume

Production volume

Cache-based Pointer Map

VDEV

Host

Host

EMC Snap creates space-saving, logical point-in-time images or “snapshots.” The snapshots are not a full copies of data; they are logical images of the original information based on the time the snapshot was created. It’s simply a view into the data. A set of pointers to the source volume data tracks is instantly created upon activation of the snapshot. This set of pointers is addressed as a logical volume and is made accessible to a secondary host that uses the point-in-time image of the underlying data.EMC Snap supports:

• Up to 16 concurrent snaps of a single source volume in open systems • Full function access to the snap; that is, the snap may also be updated with the updates residing in the Save Area

In many situations, you find yourself trying to support multiple service levels with a single solution. EMC Snap now allows you to complement existing TimeFinder environments, fulfilling multiple service level requirements while balancing the economics of the solutions.


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EMC Snap

EMC Snap captures a point-in-time view of a source volume by duplicating only the changed data:

– The target is a “slim” virtual device that contains pointers to the original source data

– The target can be mounted like any other volume– Copying only occurs when there are writes to the source

or target– The pre-image of data that has changed is copied to a

save device (common pool), consuming a fraction of the space required to copy the entire source

– Copying is controlled by copy sessions, which are created, activated, queried, listed, and terminated using the symsnap command

EMC Snap allows you to make copies of data simultaneously on multiple target devices from a single source device. The data is available to a target host instantly. You can copy data from a single source device to as many as sixteen target devices. A source device can be a Standard or BCV device. A target device is a virtual device that consumes negligible physical storage through the use of pointers to track data.


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EMC SNAP: Copying Data

Once the EMC Snap session is activated:– The first time a track on the source is written to– The original data on the source is copied to the save

device– The VDEV pointer is changed to point to the save device– The source is changed

Source VDEVWrite

toTrack

Writeto

Track

Writeto

Track

Save Device(Common Pool)

EMC Snap uses a process called “Copy on First Write” when handling writes to the production data when a snapshot is running.When a host attempts to write to the data on the production volume, the original track is first copied to the Save Area, then the write is processed against the production volume. This process of pointers maintains the consistent, point-in-time copy of the data for the ongoing snapshot.


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EMC SNAP: Striping the Save Device

Source

VDEV

Virtual Device Save Devices(Common Pool)

The copy on write is repeated every time a different track on the source is first written to Tracks are “striped” in a round-robin manner to the save devices to improve performance

The save device is not host accessible but accessed only through the virtual devices that point to it. Save devices provide a pool of physical space to store snap-copy data to which virtual devices point. These devices are striped to optimize performance when accessing the data from the common pool.


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EMC SNAP: Terminating a Copy Session

Source Save Devices(Common Pool)

When a copy session is terminated– The virtual device is made not ready– Tracks on the save device(s) are reclaimed if they are

not referenced by any other copy session– The copy session structures are freed up

VDEV

VirtualDevice

As sessions are terminated, the space in the Save Area is released and available for re-use by other sessions.


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Three Types of EMC Snap Restore

Differential Restore to the Source Device– Simply restore Save Device tracks to synchronize

Full Restore to an Independent Device– Restore all Save Device tracks– Restore all Source Device tracks unchanged from the original

point-in-time– Note: the restore target cannot be the source or target of

another snapDifferential Restore to a Split-BCV of the Source Device– Source of data is again both Save Device and Source Device– BCV tracks already identical to Source device tracks do not

need to be restored– All Save Device tracks will be restored

EMC Snap Restore•Keep all virtual sessions of the source device intact (the restored session and all other virtual sessions)•Both the virtual device and the target device are set to Not Ready for the duration of the restore•The restore creates an additional session, so can only be performed if an additional session is available•The virtual device must be set to Ready after the restore has completed•After a restore, the restore session must be terminated beforeRestoring to the Source Device•The Snap session is duplicated for the Restore, incrementing the use count for each VDEV track on the save device•Original tracks and tracks written to VDEV are copied from the save device (RESTORE_IN_PROG state)•Tracks use count is decremented but tracks remain on the save device since still referenced by original VDEV•The Symmetrix Restore session is deleted but the SE Restore session persists in a RESTORED state until terminatedRestoring to a Different Device•The Restore Target 'inherits' the pointers from the virtual device as before•Original tracks and tracks written to the VDEV are copied from the Source and Save devices (RESTORE_IN_PROG state)•Tracks use count is decremented, but tracks remain on the save device since still referenced by original VDEV(s)•The Symmetrix Restore session is deleted, but the SE Restore session persists in a RESTORED state until terminated


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EMC Snap Configuration ConsiderationsCache

– There will be some additional cache required for EMC Snap snapshots

– Total number of VDEVs (snapshots) must be accounted for in cache calculations; they count the same as a standard Symmetrix device

– Track tables for SaveDev’s are 50% larger than standard device tables

“VDEV” (snapshots)– Are persistent so small physical devices must be allocated

(1/600th the size of a source device)– Consume SYM device ID and count as a DA target– Are NOT customer configurable – Are not convertible to / from other device types (Standard /

BCV)

Additional Cache is required for Snap snapshots. The number of VDEVs must be included in the cache calculations.VDEVs are not customer configurable. Symmetrix volume limits must be respected, VDEVs consume device IDs and count as DA targets; VDEVs count towards hypervolume limits for physical devices.


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EMC Snap Configuration Considerations

“SaveDev” (Save Area)New type of device within a SymmetrixPhysical device(s) store original data copied from source on Copy on First WriteRecommendation of one SaveDev for every five snapshots that will be active at the same time (@20% change rate)SaveDev should be spread over as many physical volumes as possibleSaveDev consumes SYM device IDs and count as DA targets Track tables for SaveDevs are 50% larger than standard deviceExisting Symmetrix DMX users can use Change TrackerData is striped across entire Save Area

SaveDev (Save Area) MonitoringSaveDev thresholds can be set and notifications can be sentSaveDev can be added dynamically using Symmetrix ManagerWhen Save Area fills, all snapshots are terminated one by onePotential for rogue application to overrun all Save Area space

Symmetrix volume limits must be respected. It cannot exceed total Symmetrix budgets for either device ID limits or DA target limits. SaveDev’s consume device IDs and count as DA targets and cannot exceed hypervolume limits on physical devices since SaveDevs count towards hypervolume limits for physical devices.


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Running out of Save Device Space

Virtual Devices do not pre-allocate space for all potential copy-on-write tracksIt is possible to run out of free space on the save devicesIf a copy-on-write cannot complete due to no free space

– The target VDEV goes Not Ready (NR), applications beware!

– Copy-on-write is disabled and the source track is changed

Use symsnap monitor to track the amount of available space of the save area. The symsnap monitor command can also be used to automatically run an action if a predetermined threshold for space has been crossed. Use -percent nn –action script_pathname to specify the percentage full threshold and script associated with it.


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Snap Performance

No impact to reads on source from existence of snap volume (With no workload on target)

– Workload on target could cause disk contention with source

Write response time to protected tracks (first write to track) are higher than a normal cached write

– From < 1ms to > 10ms– Could be slightly faster if protected track is in cache– Small sequential writes less effected than large or random

writes as track is unprotected on first accessSAV device placement could be very important

– To limit the impact on performance consideration for the placement of the SAV devices must be made to reduce/remove physical device contention

EMC Snap has no impact to reads on source from existence of snap volume. Once there is activity, performance could be impacted and the target could cause disk contention with the source since it requires the source for it’s point-in-time view of production data.


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TimeFinder and Snap Impact on Source

The chart above shows the response time of an 111 LUN OLTP database running on a DMX 1000. Looking at TimeFinder, we see the initial full establish having an initial elongated response time lasting only a couple of minutes, but the synchronization of those volumes taking a considerable amount of time before the data is made available for Sequential Read Operation. Once Split, the Sequential Read Operation has no impact.Looking at Snap, we see the activate session having an initial and continued response time impact for the duration of the Sequential Read Operation, but it is immediately available. The performance impact is directly related to the resource contention between the Source and Save Devices.


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TimeFinder BCV Command Example


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● symbcv list pd displays summary information about all BCV volumes accessible to your host

● symbcv list dev displays summary information about all BCV volumes in attached Symmetrix

● A host does not need access to a BCV in order to perform TimeFinder operations on it# symbcv list pd

Symmetrix ID: 000182503423

BCV Device Standard Device Status--------------------------------- --------------------- -----------

Inv. Inv.Physical Sym RDF Att. Tracks Physical Sym Tracks BCV <=> STD--------------------------------- --------------------- -----------

c0t10d0 0B0 + 0 c1t0d1 021 0 Synchronizedc0t10d1 0B1 + 0 c1t0d0 020 0 Synchronizedc0t10d2 0B2 + 0 c1t0d2 022 0 Split c0t10d3 0B3 0 N/A N/A 0 NeverEstabc0t10d4 0B4 0 N/A N/A 0 NeverEstabc0t10d5 0B5 0 N/A N/A 0 NeverEstabc0t10d6 0B6 0 N/A N/A 0 NeverEstabTotal -------- --------

Track(s) 0 0MB(s) 0.0 0.0

Identify BCV Volumes


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# syminq

Device Product Device---------------------------- --------- ----------------- ------------------

Name Type Vendor ID Rev Ser Num Cap (KB)---------------------------- --------- ----------------- ------------------

/dev/rdsk/c0t0d0 EMC SYMMETRIX 5265 23020170 1070400/dev/rdsk/c0t0d1 EMC SYMMETRIX 5265 23021170 1070400/dev/rdsk/c0t0d2 EMC SYMMETRIX 5265 23022170 1070400/dev/rdsk/c0t0d3 EMC SYMMETRIX 5265 23023170 1070400/dev/rdsk/c0t0d4 EMC SYMMETRIX 5265 23024170 1070400/dev/rdsk/c0t0d5 EMC SYMMETRIX 5265 23025170 1070400/dev/rdsk/c0t0d6 EMC SYMMETRIX 5265 23026170 1070400/dev/rdsk/c0t0d7 EMC SYMMETRIX 5265 23027170 1070400/dev/rdsk/c0t10d0 BCV EMC SYMMETRIX 5265 230B0170 1070400/dev/rdsk/c0t10d1 BCV EMC SYMMETRIX 5265 230B1170 1070400/dev/rdsk/c0t10d2 BCV EMC SYMMETRIX 5265 230B2170 1070400/dev/rdsk/c0t1d1 R2 EMC SYMMETRIX 5265 2300A170 1070400/dev/rdsk/c0t1d2 R2 EMC SYMMETRIX 5265 2300B170 1070400/dev/rdsk/c0t15d0 EMC SYMMETRIX 5265 2310E170 5760/dev/rdsk/c0t15d1 EMC SYMMETRIX 5265 2310F170 5760

Identify Accessible BCV VolumesSyminq - Displays volume type and can also be used to identify accessible BCV volumes


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● Related devices are grouped into Device Groups– BCV devices are associated with Device Groups– All devices in a Device Group must be in the same Symmetrix ICDA– All devices in a group must be of the same type (RDF1, RDF2, Regular)– A device can only belong to a single Device Group

# symdg create -type REGULAR databasedg

# symld -g databasedg add dev 020# symld -g databasedg add dev 021# symld -g databasedg add pd c0t0d2

# symbcv -g databasedg associate pd /dev/rdsk/c1t10d0# symbcv -g databasedg associate pd c1t10d0# symbcv -g databasedg associate dev 0b2

Create Device groupAdd Physical Devices

Associate BCV devices with device group

Associating BCV Device to Device Groups


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# symdg show databasedg...Standard (STD) Devices (3):

{-----------------------------------------------------------------

Sym CapLdevName PdevName Dev Att. Sts (MB)-----------------------------------------------------------------DEV001 /dev/rdsk/c1t0d0 020 RW 1045DEV002 /dev/rdsk/c1t0d1 021 RW 1045DEV003 /dev/rdsk/c1t0d2 022 RW 1045}

......

Associated BCV Devices (3):{-----------------------------------------------------------------

Sym CapLdevName PdevName Dev Att. Sts (MB)-----------------------------------------------------------------BCV001 /dev/rdsk/c0t10d0 0B0 RW 1045BCV002 /dev/rdsk/c0t10d1 0B1 RW 1045BCV003 /dev/rdsk/c0t10d2 0B2 RW 1045}

Displaying SYMCLI Device Groups● symdg show displays detailed information about a device group

– Group membership– Gatekeepers devices– Associated BCV devices


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# symmir -g databasedg -full -opt establish

Execute 'Full Establish' operation for device group'databasedg' (y/[n]) ? y

'Full Establish' operation execution is in progress for device group'databasedg'. Please wait...

'Full Establish' operation successfully initiated for device group'databasedg'.

symmir Establish – All Devices Establishes a BCV mirror to each volume in a device groupDefault is to perform incremental establish-full must be specified the first time a BCV is established to a volume-opt Optimizes the assignment of BCV-exact assigns BCVs in order associated with DG


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● Allows you to override existing device pairing● Default is to perform incremental establish● -full must be specified the first time a BCV is established to a volume

#SYMCLI_DG=databasedg; export SYMCLI_DG

#symmir -full establish DEV003 BCV dev 0b2

Execute 'Full Establish' operation for device 'DEV003'in device group 'databasedg' (y/[n]) ? y

'Full Establish' operation execution is in progress for device 'DEV003'in group 'databasedg'. Please wait...

'Full Establish' operation successfully initiated for device 'DEV003'in group 'databasedg'.

symmir Establish – Selected Devices


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# SYMCLI_DG=databasedg; export SYMCLI_DG# symmir query -i 10 -c 10

Device Group (DG) Name: databasedgDG's Type : REGULARDG's Symmetrix ID : 000182503423

Standard Device BCV Device Status------------------------- --------------------------------- ----------

Inv. Inv.Logical Sym Tracks Logical Sym Tracks STD <=> BCV------------------------- --------------------------------- ----------

DEV001 020 0 BCV002 0B1 * 22206 SyncInProgDEV002 021 0 BCV001 0B0 * 21738 SyncInProgDEV003 022 0 BCV003 0B2 * 24208 SyncInProg

Total ------- -------Track(s) 0 68152MB(s) 0.0 2129.8

Synchronization rate : 12.6 MB/SEstimated time to completion : 00:02:49

Legend:

(*): The paired BCV device is associated with this group.

symmir querySetting the SYMCLI_DG variable eliminates having to specify the Device Group using -g flagThe [-i Interval] option displays the synchronization rate and estimated time to completion


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# symmir split

Execute 'Split' operation for device group'databasedg' (y/[n]) ? y

'Split' operation execution is in progress for device group'databasedg'. Please wait...

'Split' operation successfully executed for device group'databasedg'.

symmir SplitAll devices in a device group or specific devices can be split in a single operation-diff option can be used to specify that the split operation should initiate a differential data copy to the BCV mirror-rdf Operation is performed on the remotely associated BCV device-remote Valid only for the split of a BCV RDF1 device or for the restore from a BCV to a STD RDF2 device


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# symmir restore -full -noprompt'Full Restore' operation execution is in progress for device group‘databasedg'. Please wait...'Full Restore' operation successfully initiated for device group‘databasedg'.# symmir queryDevice Group (DG) Name: databasedg.DG's Type : REGULARDG's Symmetrix ID : 000182600534

Standard Device BCV Device Status---------------------- -------------------------------- ------------

Inv. Inv.Logical Sym Tracks Logical Sym Tracks STD <=> BCV---------------------- -------------------------------- ------------DEV001 02D 17841 BCV002 06B * 0 RestInProgDEV002 02E 22205 BCV001 06A * 0 RestInProgTotal ------- -------

Track(s) 40046 0MB(s) 1251.4 0.0

symmir restore● Data is restored from BCV to Standard Volume● Previous BCV pairing is used unless overridden with -exact option or specifying

new pairing● Default is incremental restore. Specify -full if required


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#symdg -type regular create AMdg#symdg -type regular create PMdg#symld -g AMdg addall dev -range 092:093#symbcv -g AMdg associateall dev -range 056:057#symbcv -g PMdg associateall dev -range 058:059

#symmir -g AMdg establish -full -exact#symmir -g AMdg verify -synched

All devices in group 'AMdg' are in the 'Synchronized' state.

#umount /datafs#symmir -g AMdg split -instant -noprompt

#mount /datafs#ls /datafs/AMdata AMdata10 AMdata3 AMdata5 AMdata7 AMdata9AMdata1 AMdata2 AMdata4 AMdata6 AMdata8 lost+found

● Step 5 – Details not shown● Step 6

● Step 1 – Standard devices - 092,093; BCVs - 056,057,058,059● Steps 2 – 4

Multi-BCV’s Example (from lecture)


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● Step 8

#symld -g AMdg moveall PMdg#symmir -g PMdg est -full -exact

#ls /datafs/AMdata AMdata2 AMdata4 PMdata PMdata2 PMdata4 lost+foundAMdata1 AMdata3 AMdata5 PMdata1 PMdata3 PMdata5

#umount /datafs#symmir -g PMdg split -instant -noprompt#symld -g PMdg moveall Amdg#umount /datafs#symmir -g AMdg restore#symmir -g AMdg split -noprompt#mount /datafs#ls /datafsAMdata AMdata10 AMdata3 AMdata5 AMdata7 AMdata9AMdata1 AMdata2 AMdata4 AMdata6 AMdata8 lost+found

The data “lost” from the morning run (AMdata5-AMdata10) is recovered by the restore operation. Also note that the data added in the evening run (PMdata1-PMdata5) is overwritten. Restore operation discards any changes made to the STD device and replaces it with the BCV data.

● Step 7Multi-BCV’s Example


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#symdg listD E V I C E G R O U P S

Num of Num of Num ofName Type Symmetrix ID Devices GateKeepers BCV's

AMdg REGULAR 000184501805 2 0 2PMdg REGULAR 000184501805 0 0 2

#symmir -g AMdg query -multi

Standard Device BCV Device State ------------------------- ------------------------------------ ------------

Inv. Inv. Logical Sym Tracks Logical Sym Tracks STD <=> BCV ------------------------- ------------------------------------ ------------

DEV001 092 0 BCV001 056 * 0 Split 0 N/A 058 0 Split

DEV002 093 0 BCV002 057 * 0 Split 0 N/A 059 0 Split

Multi-BCV Query


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Split Operations for Concurrent BCVs

Slit operations can be performed against the STD and the BCV1 or BCV2 pairs:

– Simultaneously Splitsymmir –g <DgName> split DEV001

– Independent Mirror Split• To target the split action at only one of the BCV devices, specify the

BCV on the command line• The other BCV will remain established with the STD

symmir –g <DgName> split DEV001 bcv ld BCV002


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Querying Concurrent BCV Status

When concurrent BCVs are part of a device group, use the –multioption as part of the query commandInvalid track tables are maintained - future concurrent incremental establish operations are possiblesymmir –g <DgName> query –multi

To evaluate the background progress after initiating a split operationsymmir –g <DgName> query –multi –bg

To verify the status of concurrent BCV pairs:symmir –g <DgName> verify -concurrent


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TimeFinder Clone Command Example


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symclone list#symdg create clonedg#symld -sid 24 -g clonedg add dev 8a src08a#symld -sid 24 -g clonedg add dev 8b tgt08b#symld -sid 24 -g clonedg add dev 8c tgt08c#symdg show clonedgGroup Name: clonedg

Number of STD Devices in Group : 3Standard (STD) Devices (3):

{-------------------------------------------------------------------- Sym CapLdevName PdevName Dev Att. Sts (MB)--------------------------------------------------------------------src08a \\.\PHYSICALDRIVE140 008A RW 449tgt08b \\.\PHYSICALDRIVE141 008B RW 449tgt08c \\.\PHYSICALDRIVE142 008C RW 449}

#symclone listSymmetrix ID: 000187400024No Copy sessions found


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symclone create#symclone -g clonedg create src08a sym ld tgt08b -noprompt'Create' operation execution is in progress for device 'src08a'paired with target device 'tgt08b' indevice group 'clonedg'. Please wait...'Create' operation successfully executed for device 'src08a'in group 'clonedg' paired with target device 'tgt08b'.

#symclone list

Symmetrix ID: 000187400024Source Device Target Device Status

------------------------- -------------------- -------------Protected

Sym Tracks Sym CG SRC <=> TGT------------------------- -------------------- -------------008A 14370 008B .X CreatedTotal --------Tracks 14370MB(s) 449.1

Legend for the Attribute of TGT Devices:(C): The background copy setting is active for this pair.(G): The Target device is associated with a device group.


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symclone activate

#symclone -g clonedg activate src08a sym ld tgt08b noprompt-'Activate' operation execution is in progress for device 'src08a'paired with target device 'tgt08b' indevice group 'clonedg'. Please wait...'Activate' operation successfully executed for device 'src08a'in group 'clonedg' paired with target device 'tgt08b'.

#symclone list

008A 14370 008B .X CopyOnAccess


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symclone -copy create, query

#symclone -g clonedg -copy create src08a sym ld tgt08c -noprompt'Create' operation successfully executed for device 'src08a'in group 'clonedg' paired with target device 'tgt08c'.

#symclone -g clonedg activate src08a sym ld tgt08c -noprompt'Activate' operation successfully executed for device 'src08a'in group 'clonedg' paired with target device 'tgt08c'.#symclone -g clonedg queryDevice Group (DG) Name: clonedgDG's Type : REGULARDG's Symmetrix ID : 000187400024

Source Device Target Device State Copy------------------------- ------------------- ------------ ----

ProtectedLogical Sym Tracks Logical Sym CG SRC <=> TGT (%)------------------------- ------------------- ------------ ----src08a 008A 7828 tgt08c 008C XX CopyInProg 45

#symclone -g clonedg query -multisrc08a 008A 0 tgt08c 008C XX Copied 100

14362 tgt08b 008B .X CopyOnAccess 0


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EMC Snap Command Example


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Monitoring Save Device Space

Use symsnap monitor to automatically run an action#symsnap -i 5 -c 2 monitor---------------------------------------------------

Device Total Used Free PercentSym Type Tracks Tracks Tracks Full---------------------------------------------------008D FBA 14370 561 13809 3%008E FBA 14370 561 13809 3%Total --------- --------- --------- ----

Tracks 28740 1122 27618 3%MB(s) 898.1 35.1 863.1


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Associate VDEV in Device Group#symdg create snapdg#symld -sid 24 -g clonedg remove src08a#symld -sid 24 -g snapdg add dev 8a src08a#symld -sid 24 -g snapdg add dev 8f vtgt08f#symdg show snapdgNumber of STD Devices in Group : 1Number of Locally-associated VDEV's : 1

Standard (STD) Devices (1):{--------------------------------------------------------------------

Sym CapLdevName PdevName Dev Att. Sts (MB)--------------------------------------------------------------------src08a \\.\PHYSICALDRIVE140 008A RW 449}

VDEV Devices Locally-associated (0):{--------------------------------------------------------------------

Sym CapLdevName PdevName Dev Att. Sts (MB)--------------------------------------------------------------------vtgt08f \\.\PHYSICALDRIVE143 008F NR 449}


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symsnap create

#symsnap listSymmetrix ID: 000187400024No Snap sessions found#symsnap -g snapdg create src08a vdev ld vtgt08f -noprompt'Snap Create' operation execution is in progress for device 'src08a'paired with target device 'vtgt08f' indevice group 'snapdg'. Please wait...'Snap Create' operation successfully executed for device 'src08a'in group 'snapdg' paired with target device 'vtgt08f'.#symsnap listSymmetrix ID: 000187400024

Source Device Target Device Status------------------------- -------------------- -------------

ProtectedSym Tracks Sym G SRC <=> TGT------------------------- -------------------- -------------008A 14370 008F X CreatedTotal --------

Tracks 14370MB(s) 449.1

Legend for the Attribute of TGT Devices:(G): The Target device is associated with a device group.


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symsnap activate

#symsnap -g snapdg activate src08a sym ld vtgt08f -noprompt

'Snap Activate' operation execution is in progress for device 'src08a'paired with target device 'vtgt08f' indevice group 'snapdg'. Please wait...'Snap Activate' operation successfully executed for device 'src08a'in group 'snapdg' paired with target device 'vtgt08f'.#symsnap list

008A 14370 008F X CopyOnWrite


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symsnap list –savedevs, query

#symsnap list –savedevs

Symmetrix ID: 000187400024Snap Save Devices

---------------------------------------------------Device Total Used Free Percent

Sym Type Tracks Tracks Tracks Full---------------------------------------------------008D FBA 14370 473 13897 3%008E FBA 14370 474 13896 3%Total --------- --------- --------- ----

Tracks 28740 947 27793 3%MB(s) 898.1 29.6 868.5

#symsnap -g snapdg query

Device Group (DG) Name: snapdgDG's Type : REGULARDG's Symmetrix ID : 000187400024

Source Device Target Device State Copy------------------------- ------------------- ---------- ------------ ----

Protected ChangedLogical Sym Tracks Logical Sym G Tracks SRC <=> TGT (%)------------------------- ------------------- ---------- ------------ ----src08a 008A 13453 vtgt08f 008F X 917 CopyOnWrite 6Total -------- ----------

MB(s) 420.4 28.7


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Thank You

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