Sharing volumes with Dynamic Provisioning

ShadowImage User Guide

Part Number

Volumes created using Dynamic Provisioning can be used as SI P-VOLs or S-VOLs.

If you are using HDP volumes as SI P-VOLs or S-VOLs, the capacity of the HDP pool allocated to the volume is added to the SI licensed capacity. A volume with capacity saving enabled can be used as a P-VOL or S-VOL.

The term Dynamic Provisioning in this manual includes Dynamic Provisioning, Dynamic Tiering, or active flash.


The following restrictions apply:

  • (VSP 5000 series) 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 copy destination volume is greater than the used capacity in the copy origination volume before capacity saving. For details, see the Provisioning Guide for your storage system.
  • If you create SI pairs using a volume for which the capacity saving function is used, compressed or deduplicated data is copied. Because of this, copy or I/O performance may be degraded.
  • When the capacity saving function is used, management information is stored in a pool. As a result, there may be 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 Dynamic Provisioning volume (DP-VOL).
    • Using the P-VOL as a DP-VOL with the Data Direct Mapping attribute, and using the S-VOL as a normal DP-VOL.
  • You cannot perform a Quick Restore if only the P-VOL or only the S-VOL is a DP-VOL or the capacity saving of the P-VOL or S-VOL is enabled. For Quick Restore, you must use DP-VOLs for both the P-VOL and S-VOL.
  • The deduplication system data volume cannot be used as a P-VOL or S-VOL.
  • You can use a maximum size Dynamic Provisioning volume as an SI P-VOL or S-VOL. For information about the maximum size for Dynamic Provisioning volumes, see the Provisioning Guide for your storage system.
  • You must use the block specification for SI volumes shared with DP-VOLs. You cannot 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.
  • (VSP 5000 series) If you downgrade to a microcode version that does not support pair creation with a DP-VOL greater than 4,194,304 MB, release the differential data (pages) managed in a pool.
  • For details about whether zero pages can be reclaimed when you specify SI P-VOLs or SI S-VOLs on Device Manager - Storage Navigator or 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 WriteSame 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 WriteSame or Unmap command processing, the pair creation may fail. In this case, create the pair again after the WriteSame or Unmap command processing finishes.
  • If the WriteSame 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.
  • SI pair creation may be rejected if the Unmap command operation is in progress with system option mode 905 ON. Wait a while, and then retry. If the operation still fails, set system option mode 905 to OFF and retry.
  • (VSP E series) 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.