Resynchronizing a UR pair

Resynchronizing a pair updates the S-VOL with differential data that accumulated since the pair was split. After the pair is resynchronized, the S-VOL is again updated from the journals.

Before you begin

  • This operation is performed from the primary storage system only.
  • The pair status must be PSUS or PSUE.

    If pair status is HOLD, HOLDING, or HLDE, use the resynchronizing mirrors operation (see Resynchronizing a mirror ).

  • In a 3DC multi-target configuration with three UR sites, you cannot resynchronize the other mirror's UR pair when one mirror's UR P-VOL is in the COPY status.
  • In a 3DC cascade configuration with three UR sites, you cannot resynchronize the UR pair between the primary and intermediate sites when the UR pair between the intermediate and secondary sites is in the COPY status, as illustrated in the following figure.
  • In a 3DC cascade configuration with three UR sites, the pair between the intermediate and secondary sites will be split automatically when you resync the UR pair between the primary and intermediate sites, if the UR pair between the intermediate and secondary sites is in the PAIR status.
  • Pairs suspended by the system (PSUE status) can be resynchronized only after the error causing the suspension has been corrected.

The following additional information might be useful before beginning the procedure:

  • In RAID Manager, use the pairresync command.
  • Performing the operation on a pair in HLDE status changes the status to HOLD.
  • The primary storage system does not resynchronize a pair that is suspended due to an error until the cause of error is resolved.
  • If P-VOL status is Failure and S-VOL status is unpaired, the pair cannot be recovered by resynchronizing. It must be deleted and created again.
  • Resynchronizing pairs when I/O load is low reduces impact on performance. Operations on multiple pairs in the same mirror with different statuses may results in suspension during periods of heavy write I/O.
  • If you resynchronize pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension could occur during the operation under heavy I/O load conditions. You can estimate whether the I/O load is heavy or not from frequency of host I/Os. This operation should be performed under light I/O load conditions.

Procedure

  1. In the Explorer pane, expand the Storage Systems tree.

  2. Expand the target storage system tree, expand Replication, and click Remote Replication.

  3. In the UR Pairs tab, select the pairs to be resynchronized and click Resync Pairs.

  4. In the Resync Pairs window, review the pairs in the Selected Pairs table. You can remove a pair from the table by selecting it and clicking Cancel.

  5. For Copy Priority list, specify the scheduling order for resynchronizing selected pairs, between 1 and 256.

  6. For Error Level, specify the system response if a failure occurs during this operation.

    • Mirror: Splits all pairs in the failed pair’s mirror.
    • LU: Splits only the specified pair or pairs that failed.

  7. Click Finish.

  8. In the Confirm window, review the settings, enter a task name, and then click Apply.

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