Backing up GAD pair volumes with ShadowImage or Thin Image Advanced provides further protection for GAD data.
Further protection for GAD data is provided in the following ways:
- When the GAD pair is resynchronized, pair status changes to COPY. While in this status, S-VOL consistency is temporarily lost. You can protect data when in COPY status by pairing the S-VOL with SI or TIA before resynchronizing the GAD pair.
- Though data in a blocked GAD pair is inconsistent, host activity can continue with the P-VOL or S-VOL. Therefore, before correcting the failure by forcibly deleting the pair, you should pair the volumes with SI or TIA.
- The SI and TIA pairs can then be copied, and the copies used for other purposes.
- The S-VOL data (backup data for a secondary operation) of a ShadowImage pair can be mirrored by sharing the S-VOL with a GAD pair. This enables you to continue a secondary operation on the other storage system if a failure occurs on one storage system. To create this configuration, set a volume for a quorum disk.
In this configuration, a ShadowImage pair is split and a GAD pair is in the PAIR status during the operations as shown in the following figure.
To update the S-VOL data (backup data for a secondary operation) of a ShadowImage pair, first suspend the GAD pair that shares the S-VOL of the ShadowImage pair. After that, resynchronize the ShadowImage pair, split the pair again, and thereby update the S-VOL data to the latest at that time. After updating the S-VOL, resynchronize the suspended GAD pair.