About Volume Copies

A volume copy is a copy of data on one volume (called a source volume) written onto another volume (called a target volume) on the same storage array. A volume copy can be used to back up data, copy data from volumes that use small-capacity drives to volumes that use large-capacity drives, and restore snapshot data to the primary volume.

A source volume accepts host input/putput (I/O) and stores application data. The target volume maintains a copy of the data from the source volume.

When you create a volume copy, the management software creates a copy pair, which defines the association between the source volume and the target volume. When you no longer need a particular volume copy, you can remove the copy pair. Removing the copy pair dissociates the source volume from the target volume and causes the target and source volumes to revert their original volume types (such as standard volume or volume snapshot), enabling them to participate in other copy pairs in different roles. Removing a copy pair does not remove the data on the target volume.

The process of creating a volume copy is managed by the redundant array of independent disks (RAID) controllers and is transparent to host machines and applications. When the volume copy process starts, the controller of the source volume reads the data from the source volume and writes it to the target volume. The volume copy has a status of In-progress while the volume copy is being completed. Up to eight volume copies can have the status of In-progress at one time.

While a volume copy has a status of In-progress, the same controller must own both the source volume and the target volume. If different controllers own the source volume and target volume before the volume copy process is started, the management software automatically transfers ownership of the target volume to the controller that owns the source volume. When the volume copy process is completed or stopped, the management software restores ownership of the target volume to its original controller owner. Similarly, if ownership of the source volume is changed during the volume copy, ownership of the target volume is also changed.

The status of a volume copy can be one of the following:

Volume Copy Status
Description
Completed
The volume copy process finished successfully.
  • The source volume is available for both read and write input/output (I/O) activity.
  • The target volume is available for read I/O activity, unless the Read-Only attribute has been set to No.
In-progress
Data is being copied from the source volume to the target volume. A maximum of eight volume copies can be in progress at one time.
  • The source volume is available for read I/O activity only.
  • The target volume is not available for read or write I/O activity.
Pending
The volume copy is waiting to be processed. If more than eight volume copies have been requested, subsequent volume copies enter a Pending state until one of the volume copies with a status of In-progress is completed.
  • The source volume is available for read I/O activity only.
  • The target volume is not available for read or write I/O activity
Failed
The volume copy process failed.
  • The source volume is available for read I/O activity only.
  • The target volume is not available for read or write I/O activity
Copy halted
The volume copy was stopped before all of the data on the source volume was copied to the target volume.

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