Dell PowerVault MD3200i - Manual (Page 18)

Figure 11. MDSM Snapshot Volume View
How SRA Uses Snapshots
The MD-Series SRA utilizes Point-in-Time Snapshots if the feature is enabled on the storage array During test failover,
the SRA creates a Snapshot Group, Snapshot Image, and Snapshot Volume on the recovery site’s storage array for all
volumes contained in the protection groups being tested. This requires the creation of the two snapshot repositories
listed above and the default size for these repositories is 10% of the base volume(s) for each repository, for a total of
20% of the base volume size. This means that the amount of free capacity on the recovery site storage array must be
20% of the base volumes participating in the test failover. This value is controlled by the SraConfigurationData.xml file
located in the config directory under the installation directory, typically:
C:\Program Files (x86)\VMware\VMware vCenter Site Recovery Manager\scripts\SAN\Dell\SraConfigurationData.xml
The value is set with the xml tag <SnapshotBasePercentage>.
<!--
SnapshotBasePercentage represents the initial size, expressed as a percentage
of volume size, of a snapshot which is formed for test failover.
-->
<SnapshotBasePercentage>10</SnapshotBasePercentage>
Depending on how the VMs are used during test failover, it is possible to fine-tune this value for your environment to
reduce the amount of free capacity needed for test failover. If the test VM residing on the recovery site ESX host does
not write extensive data to the Datastores and no synchronization (or minimal changes) occur between the protected
site volumes and the recovery site volumes during test failover, this value may be decrease to 2-5 to require even less
free capacity during test failover. The Snapshot Volume and Snapshot Group repositories are deleted during the cleanup
phase of test failover along with the Snapshot Image.
Because the Snapshot Volume is typically not used during the test failover process (little write activity), the size of these
repositories may be decreased to very small sizes in order to preserve free capacity on the recovery site’s storage
array. If a repository runs out of space during the test failover phase, the VMs on the recovery site loses access to the
Datastore and underlying volume affected by the out-of-space condition of the repository, but the protected site VM
functions as normal. These values are not recommended for Snapshot repositories used for other purposes. The sizes
and status of the repositories may be monitored from within the MDSM by selecting the All Logical Objects container
and then selecting Repositories in the drop-down box:
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