HP StorageWorks SAN Virtualization Services Platform Manager User Guide (5697-0454, May 2010)

3. Use the checkboxes to set one DPM in the DPM group as primary and one DPM as secondary.
NOTE:
If you click Finish without defining the primary and secondary DPMs, VSM defines these
roles automatically.
4. Click Next. A confirmation screen appears.
5. Click Finish. The primary and secondary Data Path Module settings are changed.
Changing the active DPM for a snapshot or VDG snapshot
If a host that is connected to VSM by two DPMs has permission to access a snapshot or VDG snapshot,
the active DPM is the DPM that is currently presenting the snapshot or VDG snapshot to the host. The
primary DPM is active unless the primary DPM fails. If the primary DPM fails, and a secondary DPM
is configured, and failover is supported on the host, the multipath software on the host triggers a
failover to the secondary DPM, because the software can no longer deliver I/Os through the failed
DPM. For information about configuring primary and secondary DPMs for the snapshot or VDG
snapshot, see “Configuring the primary and secondary DPMs per snapshot or VDG
snapshot” on page 230. You can see which DPM is currently active in the Data Path Module tab under
the snapshot or VDG snapshot list.
You can attempt to change the active DPM currently supporting the snapshot or VDG snapshot. When
you change the active DPM, the current active DPM stops servicing the snapshot or VDG snapshot
and the passive DPM takes over and becomes active. The multipath software running on the host
enables and compensates for the switch over.
This operation is not supported for a single member of a VDG or VDG snapshot. The operation is
supported for the VDG or VDG snapshot as a whole.
To change the active DPM for a snapshot or VDG snapshot:
1. Right-click the snapshot or VDG snapshot.
2. Select Manage > Manage Data Path Module > Change active Data Path Module. A confirmation
screen appears.
3. Click Finish. The active DPM is switched, unless the currently inactive DPM is not available.
Clearing persistent reservation for snapshots and VDG
snapshots
In the event that a persistent reservation cannot be cleared by normal means, you can manually clear
the persistent reservation for the holder of the persistent reservation and all registered initiators.
NOTE:
This option is only available when the snapshot is reserved and/or has registered initiators.
Clearing persistent reservation for snapshots
To clear a persistent reservation for a snapshot:
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