Splitting a Universal Replicator pair
When you split a pair, write-data is no longer sent to S-VOL and the pair is no longer synchronized. Splitting a pair or mirror gives you a point-in-time copy of the P-VOL.
Prerequisites
Pair status must be COPY or PAIR.
This operation can be performed from the primary or secondary system.
To split multiple pairs at the same time, the pairs must belong to the same mirror. This ensures sequence consistency among S-VOLs in the mirror.
Review the following information before beginning the procedure:
Splitting the pair when I/O load is low reduces impact on performance. Operations on multiple pairs in the same consistency group with different statuses might result in suspension during periods of heavy write I/O.
If you split pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension might 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.
During normal operations, the secondary system rejects write operations to an S-VOL. However, you can enable write operations to the S-VOL while the pair is split by enabling the S-VOL Write option. When this option is enabled and the split pair is resynchronized, the secondary system sends the S-VOL track bitmap to the primary system to ensure proper resynchronization of the pair to the data on the P-VOL. This S-VOL Write option is described in the pair-split procedure.
To split one or more pairs
Open the Remote Replication window:
In Hitachi Command Suite: On the Resources tab, expand the Storage Systems tree, right-click the target storage system, and click Remote Replication.
In Device Manager - Storage Navigator: In the Storage Systems tree, click Replication > Remote Replication.
Select the UR Pairs tab, and then select the pairs to be split.
From the Actions menu, click Remote Replication > Split Pairs.
In the Split Pairs window, review the pairs to be split in the Selected Pairs table. To remove a pair from the table, select the pair and click Cancel.
For Secondary Volume Write, specify whether data can be written to the S-VOL while the pair is split. This option is available only when you perform the split operation from the primary system.
Enable: The host can write data to the S-VOL while the pair is split.
Disable: The host cannot write data to the S-VOL while the pair is split.
Click Finish.
In the Confirm window, review the settings and enter a task name in the Task Name box.
Click Apply to save your settings to the system.