HP StorageWorks EVA Cluster Extension Software Administrator Guide (T3667-96045, April 2010)

links are up. Ensure that the underlying infrastructure is in a healthy state before performing live
migration.
EVA Cluster Extension has the capability of discovering unfavorable storage-level conditions for
performing live migration. In response to these conditions, EVA Cluster Extension will stop or cancel
the live migration process and inform the user. This is accomplished with no VM downtime. For
example, if live migration is initiated while VM data residing on the storage arrays is still merging
and not in sync, EVA Cluster Extension will proactively cancel the live migration and inform the user
to wait until the merge is in progress. Without this feature, live migration might fail or the VM might
come online in the remote data center with inconsistent data.
The EVA Cluster Extension StatusRefreshInterval property, which you can configure in a UCF for each
application, specifies the time interval between consecutive array status gathering operations before
the live migration to the target cluster node occurs. By adjusting this property, you can increase the
probability of getting the correct EVA array status to ensure a successful live migration. The default
StatusRefreshInterval value is 300 seconds. For more information about configuring this property, see
“Setting EVA Cluster Extension properties using a UCF” on page 45.
Using Hyper-V Live Migration with Cluster Shared Volumes is not supported with EVA Cluster Extension.
TIP:
For more information about using Hyper-V Live Migration with EVA, see the white paper Live Migration
across data centers and disaster tolerant virtualization architecture with HP StorageWorks Cluster
Extension and Microsoft Hyper-VTM on the white papers website: www.hp.com/storage/whitepapers.
Timing considerations for MSCS
EVA Cluster Extension Software gives priority to storage system operations over cluster software
operations. If EVA Cluster Extension is invoked during a DR group member resynchronization operation
(merging) or is gathering information about the remote storage system, it waits until the requested
status information is reported. This ensures the priority of data integrity over cluster software failover
behavior. However, this behavior can cause a failure of EVA Cluster Extension resources in some
cases.
• When EVA Cluster Extension uses HP SMI-S to communicate with the HP EVA storage system,
depending on the settings of the SMI-S request timeout property and the number of retries, the
online operation could time out. This can occur if the list of management servers is populated with
many management servers and the EVA storage system is busy processing other management
commands.
• When a DR group member resynchronization (merge) is in progress, the software waits until the
DR group is in a normal state if the ApplicationStartup resource property is set to RESYNCWAIT.
In case of merge/resynchronization, the delta data (stored in the history log) between the source
and destination vdisks could be large enough for the copy process to exceed the resource
PendingTimeout value.
• The values of the ResyncWaitTimeout and DataSyncTimeout properties must be less than the con-
figured resource PendingTimeout value.
In general, because the failover environment is dispersed into two (or more) data centers, the failover
time cannot be expected to be the same as that in a single data center with a single shared disk
device. Therefore, the following values of the EVA Cluster Extension resource and the service or
application using that resource, must be adjusted, based on failover tests performed to verify the
proper configuration setup: FailoverPeriod, RestartPeriod, PendingTimeout, LookAlive, and IsAlive.
Configuring EVA Cluster Extension for Windows52