Local replica options

The local replica options provide additional settings to enable you to tailor your local replication environment to your specific operating requirements. The local replica options include the Copy Threshold option that your service representative can set and the options that you can set.

Copy Threshold option

The Copy Threshold option temporarily stops copy operations when the workload of the storage system is high to prevent degradation of host I/O performance. When this option is enabled, the following copy operations are stopped:

• ShadowImage
• Thin Image
• Volume Migration
• ShadowImage for Mainframe
• Compatible FlashCopy^® V2

When you want to enable and disable the Copy Threshold option, contact your service representative.

Other local replica options

The following table lists and describes the local replica options that you can set by using Device Manager - Storage Navigator or CCI.

Note the following when you use the Quick/Steady Split Multiplexing, Reverse Copy Multiplexing, and Normal Resync Multiplexing options:

• The increase in copy volume increases the amount of data to be written to the target volume.
• If the parity group performance is less than the pair split or resync performance, the amount of data waiting to be written to cache memory (write pending ratio) may increase until it exceeds 60%, and the copy processing might be placed in the wait state. In such a case, consider the copy order to reduce the number of pairs for which copy processing is executed concurrently for volumes provisioned by the same parity group.
• If the number of volumes to be resynchronized or split increases, the maximum number of jobs for pair split or resynchronization that can execute concurrently for a pair decreases. In this case, when you split or resynchronize many pairs concurrently with this option set, the pair split or resynchronization performance might not be changed.
• The maximum number of copy operations that can be run concurrently is 126 (including the number for ShadowImage/ShadowImage for Mainframe). This number includes initial copying, resynchronization, update copying, and differential data copying. When copy operations other than pair split and resynchronization are running concurrently, if you set this option, the pair split or resynchronization performance might not be changed.
• The maximum number of pairs that can be copied concurrently in the background is 504. If the number of pairs being copied reaches 504, the next pair to be copied waits until one of the copy processing finishes.
• The Quick/Steady Split Multiplexing option is enabled for Steady Split and Quick Split.
• Reverse Copy Multiplexing is enabled for Reverse Copy.
• Normal Resync Multiplexing is enabled for Normal Resync.
• If the Increase Background Copy Performance (ShadowImage/ShadowImage for Mainframe) option is enabled, the amount of copy data increases over the entire storage system while the pair is in the PAIR status. Therefore, you can decrease the amount of differential data when the pair-split operation starts. However, the MP operating ratio and write pending rate increase because the amount of copy data increases in the storage system. Understand the trade-offs when you use this option.