One of the cool features in DeltaV Virtual Studio (DVS) is the ability to provide disaster recovery capabilities using Virtual Machine (VM) Replication. VM Replication creates and constantly updates a replica image of a running virtual machine in a separate cluster or replication server.
By locating the two clusters in different locations, a disaster in one location can be mitigated by starting up the replica image in the second location.
Now in addition to disaster recovery, virtual machine corruption can also be addressed with replication. By default, VM Replication within DVS provides two restore points, allowing recovery from an image that is up to two hours old. Here’s the procedure to increase the number of recovery points and select the required recovery point if a corruption occurs.
A couple of important points before I go on – increasing the number of recovery points increases the disk space requirements for the replica image. Also, adjusting the number of recovery points has to be done in Hyper-V, not DVS. In next year’s release of DVS, version 3.3, you’ll be able to modify the number of restore points from directly within DVS.
From the DeltaV Virtual Studio domain controller desktop, access the Hyper-V manager:
While the recovery points are associated with a replica image, managing the recovery points is done from the primary virtual machine. You can see how many recovery points (snapshots) are available by selecting the replication location and the replica virtual machine. Be sure to select the Replication tab at the bottom of the dialog box:
To change the number of recovery points, select the host and then the primary virtual machine that requires recovery point modification, then right click on the virtual machine and select Settings…
On the Settings dialog box, scroll down the left hand pane, click to expand the Replication section, then select Recovery Points:
The Recovery Points screen will show the current number of recovery points and the estimated storage requirement. Either by using the up and down arrows or by simple typing in the field, change the number of recovery points. The estimated hard drive space will change:
Once you click OK, Hyper-V will begin keeping more restore points, once an hour, until the newly entered number is achieved. Checking the replica again will show all the configured snapshots:
If a corruption is ever detected in a primary virtual machine, use the Hyper-V manager to start the replica image and pick a recovery point. DO NOT USE DeltaV Virtual Studio to start the replica – this will automatically use the most recent snapshot and will discard all the other snapshots.