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.

Before you begin

  • Required role: Storage Administrator (Remote Copy)
  • Required status: Both volumes must be simplex (unpaired).
  • The initial copy must be performed from the primary system.
  • S-VOLs must be offline to all hosts.
  • Ports must be configured for TrueCopy.
  • The primary and secondary systems must be configured for TrueCopy. See for more information.
  • The logical devices on the primary and secondary storage systems must be defined and formatted prior to pairing.
  • The P-VOL capacity and S-VOL capacity must be the same (same number of blocks). To view the capacity in blocks, click Options Capacity Unit block in the Logical Devices window. If the capacity is displayed in GB or TB, a slight difference in P-VOL and S-VOL capacity might not be displayed.
  • Stop Performance Monitor before the initial copy to avoid overloading with TCP/IP traffic.

  • In RAID Manager, use the paircreate command.
  • 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 the bullet, "When creating multiple pairs concurrently...." in the section on planning pairs and pair volumes in the TrueCopy User Guide.
  • During this operation, you can specify whether to fence the P-VOL when an error occurs. This is discussed in detail in the planning section on fence level options in the TrueCopy User Guide.
  • During this operation, you can specify the priority for initial copy operations. When performing more initial copy operations than specified for Maximum Initial Copy Activities (during configuration), see the discussion in the planning section on priority settings for initial copy operations in the TrueCopy User Guide.

Procedure

  1. Click Storage Systems, and then expand the Storage Systems tree.

  2. In the Storage Systems tree, click Replication Remote Replication.

  3. In the Remote Replication window, select the TC Pairs tab and click Create TC Pairs.

  4. In the Create TC Pairs window, for Copy Type, select TrueCopy.

  5. For Remote Storage System, select the following:

    • The Model/Serial Number and Path Group ID of the secondary system.
      Note VSP Gx00 is displayed for VSP Gx00 models and VSP Fx00 models.
    • For Path Group ID, select the path group ID.

  6. In the Primary Volume Selection box, for Selection Object, select the port type for the local storage system.

  7. In the Primary Volume Selection box, for LU Selection, select the Port ID and Host Group Name or iSCSI Target Alias. Selecting Any places all LUNs within the specified port in the Available LDEVs table. No further action is required at this time.

    NoteAvailable LDEVs limitations:
    • When using a virtual storage machine and VSP F1500, Available LDEVs displays physical LDEV information, not virtual.
    • Nondisruptive migration volumes do not display in Available LDEVs.
    NoteWhen using virtual storage machine volumes, make sure to specify the physical serial number of the storage system, not the serial number of the virtual storage machine.

  8. In the Secondary Volume Selection box, specify the following:

    1. For Base Secondary Volume, select the initial S-VOL's Port ID, Host Group ID/iSCSI Target ID, and LUN ID. If you are selecting only one P-VOL, this LU is the secondary volume. If you select multiple P-VOLs for pairing, this LUN is the base S-VOL that is assigned to the first P-VOL and from which subsequent S-VOL LUNs are assigned to the list of P-VOLs.

      CautionIn USP V/VM and VSP, LUN IDs are displayed in hexadecimal numbers. In VSP G1x00, and VSP F1500, LUN IDs display in decimal or hexadecimal numbers. If you have selected the decimal notation, when assigning an S-VOL in a USP V/VM or VSP storage system, make sure to convert the hexadecimal LUN ID number to decimal.

    2. For Selection Type, select the method for assigning S-VOLs when multiple primary volumes are selected.

      • For Interval, specify an interval the system skips between secondary system LU numbers.
      • For Relative Primary Volume, the system assigns secondary system LU numbers based on proximity to P-VOL LU numbers.

  9. Click Options to define the following optional settings:

    1. For Primary Volume Fence Level, specify whether the primary system allows or rejects write operations to the P-VOL when the pair is split due to an error.

      • Data: The P-VOL cannot be written to.
      • Status: The P-VOL can be written to if the primary system can change the S-VOL status to Suspend. If the primary system is not able to change the S-VOL status to Suspend, the P-VOL cannot be written to.
      • Never: The P-VOL can always be written to.

    2. For Initial Copy Type, specify whether to copy data from P-VOL to S-VOL during the operation.

      • Entire Volume creates the pair and copies data to the S-VOL. (Default).
      • None creates the pair but data is not copied to the S-VOL. This requires that data in the P-VOL and S-VOL are already identical.

    3. For Copy Pace, specify the number of tracks to be copied per remote I/O during the operation. The default is 15 (fast copy pace). For OPEN-V, to change the copy pace, enter a number from 1 to 4. This option affects performance as follows:

      • The speed of 1 is a slow copy pace, and is used to reduce impact on host I/O.
      • The speeds of 2 and 3 are a medium copy pace.
      • The speed of 4 is a fast copy pace, and the host I/O performance might be degraded.

      Other than OPEN-V, to change the copy pace, enter a number from 1 to 15.

      • The speeds of 1 to 5 are a slow copy pace, and are used to reduce impact on host I/O.
      • The speeds of 6 to 10 are a medium copy pace.
      • The speeds of 11 to 15 are a fast copy pace, and the host I/O performance might be degraded.

    4. For Initial Copy Priority, specify the scheduling order for the initial copy operation. The range is 1-256, and the default is 32.

      If you perform initial copy operation over the number of times set for Maximum Initial Copy Activities in the Edit Remote Replica Options window, you can set the order (priority) for the additional initial copy operations.

      The initial copy priority is determined within the range of the number of initial copy operations performed concurrently. Because of this, the additional initial copy operations are not performed until the first batch completes.

      If a time-out error occurs during this operation, the order specified in Initial Copy Priority may not run as expected. A time-out error can occur because of the CU configuration or data path error. Review the error, delete the pair with an error, and then retry the operation.

  10. Back again in the Primary Volume Selection box, select the primary volume to be copied first and click Add. The volume and pair information moves to the Selected Pairs table.

    In the Selected Pairs table, you can change pair options by selecting it and clicking Change Settings. Remove a pair by selecting it and clicking Remove.

  11. Click Finish.

  12. In the Confirm window, review the settings and enter a task name in the Task Name box.

  13. Click Apply to save your settings.

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