HP StorageWorks SAN Virtualization Services Platform 3.0 release notes (5697-0404, April 2010)

• Do not overload the array that contains the setup virtual disks. An overloaded array is one where
the average write response time for the VSM setup virtual disk exceeds 20 msec.
• The default threshold for capacity alerts is 10%. When setting capacity alerts, you should set the
alerts slightly higher (for example, add 5%) to ensure that the storage administrator is notified in
time.
• Once a synchronous mirror is created, you cannot change the LU number of a synchronous mirror
group.
• You cannot add synchronous mirroring to a member of an asynchronous mirror group due to the
existence of the asynchronous PiTs. However, you can first create a synchronous mirror and then
add the asynchronous mirror group to it.
• It is recommended that the quorum disk always be in automatic failover (Continue on fail) mode.
Operational best practices
• Should you want to delete, remove, or undo an operation to an SVSP entity, it is best if you reverse
the processes that were used to get you to that operational stage. Additional details are in the HP
StorageWorks SAN Virtualization Services Platform administrator guide.
For example, you have I/O to a snapshot created from a PiT that was created from a virtual disk
(that is online to a different application). Assume the following steps were performed to get to this
stage:
1. A virtual disk is created from a pool.
2. The virtual disk is presented to a host.
3. The first I/O stream is initiated to the virtual disk.
4. A PiT is created from the virtual disk.
5. A snapshot is created from the PiT.
6. The snapshot is presented to a host.
7. The second I/O stream is initiated to the snapshot.
If you decide to delete the virtual disk, you should remove or halt all the operations that were
performed from the time the virtual disk was created, by working backwards. In this case the
process would be:
1. Halt the second I/O stream to the snapshot (initiated in step 7 above).
2. Unpresent the snapshot to its host (presented in step 6 above).
3. Delete the snapshot (created in step 5 above).
4. Delete the PiT (created in step 4 above).
5. Halt the first I/O stream to the virtual disk (initiated in step 3 above).
6. Unpresent the virtual disk to its host (presented in step 2 above).
7. Delete the virtual disk (created in step 1 above).
Carrying this example further, if you decide to delete the pool from which virtual disks are created,
you must delete all the virtual disks in that pool. This requires that you delete or halt all operations
being performed on or by those virtual disks, like I/O, snapshots, PiTs, presentations, and so on.
• HP recommends that you limit the number of virtual disks in a pool to 500, with a maximum limit
of 1000. In addition, avoid creating virtual disks that span more than one pool.
• Do not remove a single snapshot from a virtual disk group snapshot set.
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