Creating pairs

You create TrueCopy pairs to maintain an up-to-date copy of data in a volume.

When you create a pair, the initial copy operation copies all data in the P-VOL to the S-VOL. The P-VOL remains available to the host for I/O operations during the initial copy operation.

• During this operation, you select P-VOLs and S-VOLs by port ID, Host Group ID or iSCSI Target ID, LUN, CU, and/or LDEV numbers.
• During this operation, you can specify multiple P-VOLs to be paired, but only one S-VOL. To plan how the system assigns subsequent S-VOLs, see Pair volume requirements and recommendations.
• During this operation, you can specify whether to fence the P-VOL when an error occurs. This is discussed in detail in Allowing I/O to the P-VOL after a split: Fence Level options.
• During this operation, you can specify the priority for initial copy operations.
• When any of the following conditions occur during TC pair duplication, sometimes the TC pair splits to prioritize refresh I/O rather than TC pair duplication.
  • The MP unit processor operation rate which the P-VOL belongs is 70% or higher in the primary system.
  • Refresh I/O inflow for the P-VOL is large in the primary system.
  • MP unit write-pending which S-VOL belongs is 65% or higher in the secondary system.
• When creating or resynchronizing TC pairs, be aware of the load of the storage systems at each site.
• When you create (or resynchronize) a TC pair, the operation might fail if the controller board is blocked on the primary or secondary storage system. If it is blocked, restore the controller board and then create the pair.