HP StorageWorks SAN Virtualization Services Platform 3.0.1 Release Notes (5697 - 0405, May 2010)

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.
• Do not change any back-end logical unit characteristic (for example, number, name, size [by ex-
panding or contracting], and so on) once it has been virtualized (for example, entered into a VSM
storage pool) or is being managed by the VSM. The LUN identification has been written on the
LU by VSM.
• Before starting a migration task, make sure the task does not have any PiTs (such as user PiTs or
mirror PiTs). If PiTs exist, they must be deleted before the task starts, otherwise a future snapshot
created on these PiTs (or a rollback to them) after migration will not be consistent.
• Before installing or uninstalling VSM, you must make sure that all iSCSI connections are disconnec-
ted and the VSM is disconnected from the SAN. You must log out of all existing iSCSI connections.
• After a disruption (perturbation) of VSM connections, wait at least two minutes to let the VSM re-
discover all paths.
• When booting from the SAN, make sure the host only sees that LUN through one path when there
is no multipathing software on the host.
• When rebooting one DPM, wait at least 30 minutes before rebooting the other DPM.
• Before disconnecting a VSM server from the domain, ensure that the other VSM server is running.
There is an increased risk of a Windows fault when disconnecting (even partially) a VSM server
from the domain (for example, to perform maintenance). The lack of an operational second VSM
server can lead to I/O failure. Additionally, HP recommends that you use the Failover VSM option
from the Tools > Maintenance menu in the SVSP GUI to ensure the VSM is passive before discon-
necting a VSM server.
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