Split BCV’s

December 2nd, 2008 No comments

Based on the Timfinder BCV’s you split for backup or any other purposes, here is the info you need to figure how how to mount them or use them within your symm.

The issue revolves around the volume or disk group header information. Conceptually, this is the same for both Veritas Volume manager and HP’s Logical Volume Manager. Both volume managers store information about the volume/disk group on the disks that comprise the group. So, when you split off the BCVs, the information encoded is the exact same as the information on the standard devices. There won’t be a separate volume/disk group, LV/volume to mount because everything thinks its the same thing.

So, you have to figure a way around that. Fortunately, there’s a way for both HP’s Logical volume manager and Veritas’ Volume manager.

HP Logical volume manager – vgchgid

1. Split the BCV’s from the Symmetrix disk group. Example
1. /dev/dsk/c2t0d0
2. /dev/dsk/c2t1d0
3. /dev/dsk/c3t0d0
4. /dev/dsk/c3t1d0

2. Create an array with the appropriate disk names. Creating an array is optional.

set -A bcvs /dev/dsk/c2t0d0 /dev/dsk/c2t1d0 /dev/dsk/c3t0d0 /dev/dsk/c3t1d0

3. Create an vgexport map file for the volume group – particularly if you’re using nonstandard logical volume names.

vgexport -p -m /tmp/${vg}.map

4. Create the new volume group directory structure as needed:

mkdir /dev/vgbcv
mknod /dev/vgbcv/group c 64 0x0#0000

5. Change the volume group header information on all the BCV disks simultaneously:

/usr/sbin/vgchgid ${bcvs[*]}

6. Import the new volume group

vgimport -m /tmp/${vg}.map vgbcv ${bcvs[*]}

7. Mount the filesystems and do with them as you will.

Steps to import the clone disk (including EMC BCVs) using VxVM 5.0 :

1) before we split the BCV device from vm240dg (as in example below), “vxdisk list” shows the clone disk in an error udid_mismatch status

EMC0_1 auto:cdsdisk EMC0_1 vm240dg online
EMC0_27 auto – – error udid_mismatch

2) then issue the following command to split the BCV device

/usr/symcli/bin/symmir -g vm240dg split DEV001

3) after we split the BCV device DEV001 from vm240dg, we need to issue “vxdctl enable” or “vxdisk scandisks” to update the configuration in order to see the clone disk is in “online udid_mismatch” state issuing “vxdctl enable” ( or “vxdisk scandisks”), and “vxdisk list” gives the following display

EMC0_1 auto:cdsdisk EMC0_1 vm240dg online
EMC0_27 auto:cdsdisk – – online udid_mismatch

4) use the following comand to import the clone disk

vxdg -n newdg -o useclonedev=on -o updateid import vm240dg

5) issue “vxdisk list” to see the clone disk is imported

EMC0_1 auto:cdsdisk EMC0_1 vm240dg online
EMC0_27 auto:cdsdisk EMC0_1 newdg online clone_disk

SRDF Commands

December 2nd, 2008 1 comment

The following are SRDF Commands and what they are used for.

Composite SRDF commands

1. Failover:
1. Actions:
1. Write disables (WD) R1
2. Sets link to Not Ready (NR)
3. Write enables R2
2. Command:

symrdf -g ${group} failover

2. Update: Helps to speed up the failback operation by copying invalid tracks before write disabling any disks.
1. Actions:
1. Leaves service state as is.
2. Merges the tracks
3. Copies invalid tracks
2. Command:

symrdf -g ${group} update

3. Failback:
1. Actions:
1. Write disables R2
2. Suspends RDF link
3. Merges the disk tracks.
4. Resumes the link
5. Write enables R1
6. Copies the changed data
2. Command:

symrdf -g ${group} failback

4. Split: Leaves both R1 & R2 in write enabled state.
1. Actions:
1. Suspends the rdf link.
2. Write enables R2
2. Command:

symrdf -g ${group} split

5. Establish:
1. Actions:
1. Write disables R2
2. Suspends the rdf link
3. Copies data from R1 to R2
4. Resumes the rdf link.
2. Command:

symrdf -g ${group} [ -full ] establish

6. Restore: Copies data from R2 to R1
1. Actions:
1. Write disables both R1 & R2
2. Suspends the rdf link.
3. Merges the track tables
4. Resumes the rdf link.
5. Write enables R1
2. Command:

symrdf -g ${group} [ -full ] restore

Singular SRDF commands
1. Suspend: symrdf -g ${group} suspend
2. Resume: symrdf -g ${group} resume
3. Set mode: symrdf -g ${group} set mode sync
symrdf -g ${group} set domino on
symrdf -g ${group} set acp_disk skew 1000

EMC Timefinder Commands

December 2nd, 2008 No comments

The following are the Timefinder Procedural Commands

It outlines everything that needs to be done from start to finish. Realize that for routine operations, some of these steps won’t be needed; however, for the sake of completeness.

Prepare EMC structures

1. Create a Symmetrix disk group

symdg -t [ Regular | RDF1 | RDF2 ] create ${group}

2. Add devices to the disk group

symld -g ${group} add pd /dev/dsk/c#t#d#
symld -g ${group} add dev 01a

3. Associate BCV devices to the disk group

symbcv -g ${group} associate pd ${bcv_ctd}
symbcv -g ${group} associate dev ${bcv_dev}

Establish BCV mirrors

1. ID the logical device names: Timefinder defaults to using the logical device names. You can id the logical device names by:

symmir -g ${group} query

2. First time establish, execute a full establish:

symmir -g ${group} -full establish ${std_log_dev} bcv ${bcv_log_dev}

3. Use symmir query to monitor progress.

symmir -g ${group} query

Break BCV mirrors

1. Types of splits:

1. Instant split: Split is performed in the background after the completion of the split I/O request.
2. Force split: Splits the pair during establish or restore operations; invalid tracks may exist.
3. Reverse split: Resyncs the BCV with the full data copy from its local or remote mirror.
4. Reverse differential split: Enables a copy of only out-of-sync tracks to the BCV from its mirror.
5. Differential split: Enables a copy of only the updated tracks to the BCV’s mirror.

2. Commands:

symmir -g ${group} split
symmir -g ${group} split -instant
symmir -g ${group} split -differential
symmir -g ${group} reverse split -differential

Reestablish or restore BCV mirrors

1. Restore copies data from BCV back to standard pair. >Reestablish, on the other hand, does a differential update of the BCV from the standard device.

2. Commands:
symmir -g ${group} establish Differential reestablish from standard device to BCV
symmir -g ${group} -full restore Full restore of all tracks on BCV to standard device.
symmir -g ${group} restore Differential restore of BCV data to standard device.

The Timefinder Strategies are as follows

1. Maintain BCV mirrors with the standard device; break the mirrors when you want to backup, test, or develop on a copy of the original.

This is probably the most common way of running Timefinder. The advantage is that the split operation will happen almost instantly as the mirrors are fully synced all the time. The disadvantage is that anything towards that happens to the standard device will be reflected in the BCV mirror.

2. Maintain the BCV as a split device to keep an online backup of the original data.

Symcli Basic Commands

December 2nd, 2008 No comments

Following are the Symcli Commands

You can use the man pages for further info.

You can also use the option symxxx -h and will help you navigate around.

Most of the commands come in flavors of three as follows:

Reference Description Example
pd Physical device name /dev/dsk/c3t4d5
dev Symmetrix device name 0FF
ld Symmetrix logical device name DEV001

Examples are as follows:

1. symdev list
2. sympd list
3. symld -g ${group} list

Command Note
symdev Performs operations on a device given the Symmetrix device name.
sympd Performs operations on devices given the devices physical name (c2t0d0)
symgate Performs operations on gatekeeper devices.
symdg Performs operations on Symmetrix device groups
symld Performs operations on devices within a device group
symbcv Performs support operations on BCV pairs
symmir Performs control operations on BCV pairs
symrdf Performs control operations on RDF pairs
symcfg discover Creates a local database of the attached symmetricies.
syminq Shows internal & external devices that the host sees.