Notes on using DP-VOLs

The supported Volume Migration operations differ depending on the status of the pool to which the target DP-VOL belongs. In some cases, Volume Migration cannot be performed.

The following table shows the available Volume Migration operations for each combination of source and target volumes.

The following table shows whether Volume Migration operations are available for each status of capacity expansion.

• If you create a Volume Migration pair by using a DP-VOL whose capacity is larger than 4,194,304MB (8,589,934,592 block), the differential data is managed in the pool to which the migration source and target volumes are associated. In this case, a maximum of four pages are required as the pool capacity for data managing differences, for each unit (4,123,168,604,160 bytes) of the volume.
• When you create a Volume Migration pair by using a DP-VOL whose capacity is larger than 262,668 cylinders, the differential data is managed in the pool that the source and target volumes of the Volume Migration pair are associated with. In this case, one page of pool capacity is required for the differential data for each 4,096 cylinders of volume capacity.
• If you create a Volume Migration pair during the processing of reclaiming zero data (including reclaiming zero data by the Write Same/Unmap command or rebalancing), the processing of reclaiming zero data will be suspended.
• If reclaiming zero pages is in progress on a source or target volume during Volume Migration pair creation, the pair might not be created. Therefore, to create a pair, avoid the time period when reclaiming zero pages is in progress.
• If the Write Same/Unmap command is issued for the source or target volume of the Volume Migration pair, the processing of reclaiming the zero data, by the Write Same/Unmap command, is not performed.
• Even if rebalancing operates, the processing of reclaiming zero data by rebalancing is not performed for the source or target volume of the Volume Migration pair.
• When you use a standard volume or an external volume as the source volume and a DP-VOL as the target volume, pages are allocated to the entire area of the DP-VOL (target volume).
• When you use a DP-VOL as the target volume and the pool to which the target volume belongs is full, the migration of the volume fails. Confirm that the pool to which the target volume belongs has sufficient free space, and then migrate the volume.