Dell PowerVault MD3820f - Manual (Page 187)

NOTE: If the snapshot virtual disk that is used as the copy source is active, the source virtual disk
performance degrades due to copy-on-write operations. When the copy is complete, the snapshot
is disabled and the source virtual disk performance is restored. Although the snapshot is disabled,
the repository infrastructure and copy relationship remain intact.
Creating A Virtual Disk Copy For An MSCS Shared Disk
To create a virtual disk copy for a Microsoft Cluster Server (MSCS) shared disk, create a snapshot of the
virtual disk, and then use the snapshot virtual disk as the source for the virtual disk copy.
NOTE: An attempt to directly create a virtual disk copy for an MSCS shared disk, rather than using a
snapshot virtual disk, fails with the following error: The operation cannot complete because the
selected virtual disk is not a source virtual disk candidate.
NOTE: When creating a snapshot virtual disk, map the snapshot virtual disk to only one node in the
cluster. Mapping the snapshot virtual disk to the host group or both nodes in the cluster may cause
data corruption by allowing both nodes to concurrently access data.
Virtual Disk Read/Write Permissions
After the virtual disk copy is complete, the target virtual disk automatically becomes read-only to the
hosts. The target virtual disk rejects read and write requests while the virtual disk copy operation has a
status of Pending or In Progress or if the operation fails before completing the copy. Keep the target
virtual disk Read-only enabled if you want to preserve the data on the target virtual disk for reasons such
as the following:
• If you are using the target virtual disk for backup purposes.
• If you are using the data on the target virtual disk to copy back to the source virtual disk of a disabled
or failed snapshot virtual disk.
If you decide not to preserve the data on the target virtual disk after the virtual disk copy is complete,
change the write protection setting for the target virtual disk to Read/Write.
Virtual Disk Copy Restrictions
Before you perform any virtual disk copy tasks, understand and adhere to the restrictions listed in this
section. The restrictions apply to the source virtual disk, the target virtual disk, and the storage array.
• While a virtual disk copy has a status of In Progress, Pending, or Failed, the source virtual disk is
available for read I/O activity only. After the virtual disk copy is complete, read and write I/O activity to
the source virtual disk are permitted.
• A virtual disk can be selected as a target virtual disk for only one virtual disk copy at a time.
• A virtual disk copy for any virtual disk cannot be mounted on the same host as the source virtual disk.
• Windows does not allow a drive letter to be assigned to a virtual disk copy.
• A virtual disk with a Failed status cannot be used as a source virtual disk or target virtual disk.
• A virtual disk with a Degraded status cannot be used as a target virtual disk.
• Snapshots created using older (legacy) premium feature versions cannot be managed using newer
snapshot premium feature options. A virtual disk in a snapshot group cannot be a target for a virtual
disk copy.
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