Reverse resynchronization

You can use one of the following methods to restore pairs:

• Reverse Copy (Secondary > Primary): A full restoration from the S-VOL to the P-VOL. The differential data is updated to the P-VOL.

  During a Reverse Copy you can delete or suspend the pairs, but you cannot create, split, or resynchronize pairs that share the same P-VOL. The P-VOL is inaccessible to hosts.

  If you are sharing a TC or UR volume with an SI volume, you cannot create a TC or UR pair with the shared volume.

  You cannot use Reverse Copy with an SI L2 pair.

• Quick Restore (Secondary > Primary): A partial restoration that does not copy the data but does the following:
  • Swaps the P-VOL and S-VOLs including their RAID levels and drive types.
  • Pairs the volumes (PAIR status*).

    *The pair status changes to COPY(RS-R)/RCPY first, and then it changes to PAIR.

  • Exchanges the P-VOL and S-VOL encryption statuses if an SI pair consists of encrypted volumes and a nonencrypted volume.
  CAUTION:
  To prevent the two volumes from being swapped, the P-VOL and S-VOLs must be assigned to the same cache logical partition (CLPR).

  During a Quick Restore, the P-VOL and S-VOL are inaccessible. After a Quick Restore, the P-VOL is accessible.

  Best Practice: If you have a small amount of differential data, use Reverse Copy instead of Quick Restore, since Reverse Copy completes faster.

  If you use volumes for which you set Data Retention Utility access attributes, Quick Restore does not exchange the P-VOL and S-VOL access attributes.

  For more information about using volumes for which you set Data Retention Utility access attributes, see Sharing volumes and Data Retention Utility access attributes.

  Note: HDvM - SN can show outdated information after a Quick Restore. To show the latest information, click Refresh View.
  Note: To minimize the time it takes to Quick Restore an SI pair, do not perform LDEV maintenance while the Quick Restore is processing.

  You can delete or suspend the pair while you are restoring the pair using Quick Restore but you cannot do the following:

  • Create, split, or resynchronize pairs that share the same P-VOL.
  • Create a TC or UR pair with a volume shared by SI.

  You cannot Quick Restore the following pairs:

  • An SI L2 pair
  • A pair volume for which you are formatting either internal volume using Quick Format.

    For more information about formatting volumes using Quick Format, see the Provisioning Guide for your storage system.

  • A pair in which one volume is a DP-VOL, though not both.
  • The capacity saving of either P-VOL or S-VOL is enabled.
  • An SI S-VOL you are sharing with an HTI volume.

  By default, for pair resynchronization (Normal Resync or Reverse Copy), the maximum multiplicity of copy processing for each pair is set to 24. However, if you set the Normal Resync Multiplexing option or Reverse Copy Multiplexing option of local replica options to OFF, the multiplicity can be changed to 1. Make sure to set the Normal Resync Multiplexing option or Reverse Copy Multiplexing option to OFF if the host I/O performance is prioritized. These local replica options can be set by using HDvM - SN or CCI.