Data-reduced volumes* can be used as SI P-VOLs or S-VOLs.
* On VSP One B85, a data-reduced volume is a DRS-VOL. On VSP One B20 series, a data-reduced volume is a V-VOL with capacity saving enabled.
If you are using DP volumes as SI P-VOLs or S-VOLs, the capacity of the DP pool allocated to the volume is added to the SI licensed capacity. A V-VOL with capacity saving enabled can be used as a P-VOL or S-VOL.
Restrictions
- Data compressed or deduplicated by the capacity saving function is copied to a volume after compression and deduplication are released. The capacity saving function is not performed immediately for copied data. Before creating or resynchronizing a ShadowImage pair, make sure that the available capacity in the target copy volume is greater than the used capacity in the source copy volume before capacity saving. For details, see the Provisioning Guide.
- If you create a ShadowImage pair using a data-reduced volume, compressed or deduplicated data is copied. Because of this, copy or I/O performance might be degraded.
- When the capacity saving function is used, management information is stored in a pool. As a result, there might be a difference between a P-VOL and an S-VOL in the number of used pages or licensed capacity.
- Because the S-VOL uses the same pool capacity as the P-VOL, best practice is to avoid the following volume combinations:
- Using only the S-VOL as a DP-VOL.
- Using a P-VOL that is a DP-VOL with the Data Direct Mapping attribute with an S-VOL that is a normal DP-VOL.
- (VSP One Block 20 series) You cannot perform a Quick Restore if capacity saving is enabled for the P-VOL or S-VOL.
- (VSP One Block 85) You cannot perform a Quick Restore in any of the following conditions:
- Only the P-VOL is a DP-VOL.
- Only the S-VOL is a DP-VOL.
- A DRS-VOL is used for either of the P-VOL or the S-VOL.
- A DSD-VOL cannot be used as a P-VOL or S-VOL.
- You must use the capacity in blocks for SI volumes shared with DP-VOLs. Do not use TB, GB, or MB. For example, 4 TB = 8,589,934,592 blocks.
- When you create an SI pair using a DP-VOL greater than 4,194,304 MB (8,589,934,592 blocks), the differential data is managed in a pool associated with the SI pair volume. In this case, the required pool capacity for managing the differential data varies depending on the product configuration, with a maximum of four pages for every 4,123,168,604,160 bytes.
- For details about whether zero pages can be reclaimed when you specify SI P-VOLs or SI S-VOLs on Command Control Interface, see the Provisioning Guide for your storage system.
- If you perform an SI paircreate or pairresync operation while zero pages are being reclaimed (including operations by Write Same or Unmap, or by rebalancing the usage level), it results in zero-page reclamation interruption.
- If reclaiming zero pages is in progress on a P-VOL or an S-VOL during SI pair creation, the pair might not be created. Therefore, avoid the time period when reclaiming zero pages is in progress when creating a pair.
- If you create an SI pair during Write Same or Unmap command processing, the pair creation may fail. In this case, create the pair again after the Write Same or Unmap command processing finishes.
- If the Write Same or Unmap command was issued to the SI P-VOL or S-VOL, zero pages are not reclaimed by the command.
- Zero pages are not reclaimed for the SI P-VOL or S-VOL even if you rebalance the usage level.
- If the copy origination page of an SI pair is not allocated, but the copy destination page is already allocated, zero data is copied to the copy destination. In this case, zero data pages are not reclaimed. If you want to reclaim zero data pages, split the SI pair to change its status to PSUS, and then reclaim zero data pages of the applicable volume.