Using the Disk Group Split and Join feature


Using the Disk Group Split and Join feature
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The Disk Group Split and Join feature of Veritas Volume Manager enables you to synchronize the Secondary. For more information on the Disk Group Split and Join feature, refer to the Symantec Storage Foundation Administrator's Guide. To set up replication using this method, ensure that you have a valid Disk Group Split and Join license on your system.

Linked break-off snapshots are another preferred method for off-host processing. Linked break-off snapshots are a variant of third-mirror break-off snapshots, which use the vxsnap addmir command to link a specially prepared volume with the data volume. You prepare the volume that is used for the snapshot in the same way you do for full-sized instant snapshots. However, unlike full-sized instant snapshots, you can set up this volume in a different disk group from the data volume. This makes linked break-off snapshots especially suitable for recurring off-host processing applications because it avoids the disk group split/join administrative step.

See Example for setting up replication using Disk Group Split and Join.

To synchronize the Secondary using Disk Group Split and Join

Create a snapshot plex for each data volume in the Primary RVG by issuing the following command on the Primary:
```
# vxassist -g diskgroup snapstart dv_name
```
You can use the -b option with the vxassist snapstart command to run the command in the background. Note that if you use the -b option of the vxassist snapstart command, you must wait for the snapshot plexes for all the data volumes in the RVG to be created and synchronized completely before you proceed to the next step. When the plex synchronization completes, the output of the vxprint command displays the state of the new snapshot plex as SNAPDONE.
Start a Primary Storage Checkpoint by issuing the following command on the Primary:
```
# vxrvg -g diskgroup -c checkpt_name checkstart \
local_rvgname
```
Take a snapshot of each data volume in the Primary RVG by issuing the following command on the Primary:
```
# vxrvg -g diskgroup snapshot local_rvgname
```
End the Storage Checkpoint by issuing the following command on the Primary:
```
# vxrvg -g diskgroup checkend local_rvgname
```
Split the snapshot volumes into a new disk group by issuing the following command on the Primary:
```
# vxdg split diskgroup new_diskgroup SNAP-dv_name ...
```
Rename each snapshot volume in the new disk group with the same name as the corresponding data volume in the Primary RVG by issuing the following command on the Primary:
```
# vxedit -g new_diskgroup rename SNAP-dv_name dv_name
```
Deport the split-off disk group, rename it to the same name as the disk group of the Primary RVG, and change the ownership of the split-off disk group to the Secondary host so that it may be automatically imported on the Secondary on reboot.
```
# vxdg -n diskgroup -h sec_hostname deport new_diskgroup
```
The argument sec_hostname is the name of the Secondary host displayed in the output of the uname -a command.
Physically remove the disks contained in the deported disk group by following the procedures recommended by the disk manufacturer; then attach the disks to the Secondary host.
On the Secondary, import the disks that were moved over from the Primary if not already imported:
```
# vxdg import diskgroup
```

Add the Secondary to the RDS by issuing the following command on the Primary:

# vradmin -g diskgroup addsec local_rvgname pri_hostname   \ 
     sec_hostname

Start replication by issuing the following command from any host in the RDS:
```
# vradmin -g diskgroup -c checkpt_name startrep \
    local_rvgname sec_hostname
```
The argument sec_hostname is the name of the Secondary host displayed in the output of the vradmin printrvg command. If the RDS contains only one Secondary, the sec_hostname is optional.

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