Dell PowerVault ME4 Series Storage System Administrator’s Guide

Copying a volume or snapshot

You can copy a linear or virtual volume or a virtual snapshot to a new virtual volume.

When using a linear volume as the source, the copy operation creates a transient snapshot, copies the data from the snapshot, and deletes the snapshot when the copy is complete. If the source is a snapshot, the copy operation is performed directly from the source; this source data may change if modified data is to be included in the copy and the snapshot is mounted and in use.

To ensure the integrity of a copy, unmount the source or, at minimum, perform a system cache flush on the host and refrain from writing to the source. Since the system cache flush is not natively supported on all operating systems, it is recommended to unmount temporarily. The copy will contain all data on disk at the time of the request, so if there is data in the OS cache, that data will not be copied. Unmounting the source forces the cache flush from the host OS. After the copy has started, it is safe to remount the source and resume I/O.

To ensure the integrity of a copy of a virtual snapshot with modified data, unmount the snapshot or perform a system cache flush. The snapshot will not be available for read or write access until the copy is complete, at which time you can remount the snapshot. If modified write data is not to be included in the copy, then you may safely leave the snapshot mounted. During a copy using snapshot modified data, the system takes the snapshot off line.