Skip to main content

We've Moved!

Product Documentation has moved to docs.hitachivantara.com
Hitachi Vantara Knowledge

TC pair operations

You perform different tasks on TrueCopy pairs in day to day operations as a Storage Administrator.

Pair operations workflow

You must have Storage Administrator (Remote Copy) role to perform TrueCopy operations.

GUID-B0D31750-26F6-4CE0-B19C-62707C89F2F9-low.png

Basic TrueCopy operations consist of the following operations.

  • Check prerequisites for each procedure.
  • Always check pair status. Each TrueCopy operation requires the pair to be in a specific status.
  • Create a pair, in which the S-VOL becomes a duplicate of the P-VOL.
  • Split a pair, which separates the P-VOL and S-VOL and allows read/write access to the S-VOL if desired.
  • Resynchronize a pair, in which the S-VOL again mirrors the on-going, current data in the P-VOL.
  • Delete a pair.
Note
  • To perform pair operations or check the pair status in HDvM - SN, LU paths must be established for the target volume.
  • Pair operations cannot be performed when changing the firmware, nor if firmware changes are cancelled. If you start a firmware change, make sure it is complete before performing pair operations. You can perform pair operations from CCI even while changing the firmware or when firmware changes are canceled.
  • 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.

Checking pair status

Every TrueCopy operation requires that the pairs have a specific status. Before performing any operation, check the pair status.

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.
  • (VSP 5000 series) Ports must be configured for TrueCopy. See Defining port attributes (VSP 5000 series) for more information.
  • The primary and secondary systems must be configured for TrueCopy. See Adding remote connections 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.

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. (VSP 5000 series) In the Create TC Pairs window, for Copy Type, select TrueCopy.

    GUID-B7FFEACB-460E-4448-9DF5-651F89A31536-low.png
  5. For Remote Storage System, select the following:

    • The Model/Serial Number and Path Group ID of the secondary system.
    • For Path Group ID, select the path group ID.
  6. (VSP Gx00 modelsand VSP Fx00 models, VSP E series) 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.
    • (VSP 5000 series) 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 VSP, LUN IDs are displayed in hexadecimal numbers. In VSP 5000 series, LUN IDs display in decimal or hexadecimal numbers. If you have selected the decimal notation, when assigning an S-VOL in a 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.

      (VSP 5000 series) 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.

Splitting pairs

You split TrueCopy pairs when you migrate data, when you recover data, or when you perform tasks on TrueCopy pairs, like assigning pairs to consistency groups.

Splitting pairs suspends data copying to the S-VOL.

When you split a pair, the following occurs:

  • I/O writes from the host continue to the P-VOL, but stop to the S-VOL.
  • Any current update copy operation completes to the S-VOL, ensuring data consistency to the point of the split operation.
  • Pair status changes to PSUS.
  • The primary system records the updated tracks to the P-VOL that occur after the split as differential data. This data is copied to the S-VOL when the pair is resynchronized.
  • (VSP Gx00 modelsand VSP Fx00 models, VSP E series) To access an S-VOL of which write option is enabled, the pair must be split.
  • (VSP Gx00 modelsand VSP Fx00 models, VSP E series) When a pair is split, the secondary storage system completes pending copy operation before changing the pair status to ensure pair synchronization.
  • You can set an option to block updates to the P-VOL while the pair is split. This results in the P-VOL and S-VOL staying synchronized.
  • Another option is to enable system write to the S-VOL from a host. The secondary system records the updated tracks as differential bitmaps. When the pair is resynchronized, the secondary system sends the differential bitmaps to the primary system, which merges all differential bitmaps to determine which tracks are out-of-sync.

Before you begin

  • Required role: Storage Administrator (Remote Copy)
  • Required status: Pair status must be COPY or PAIR

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, click the TC Pairs tab, and then select the pair to be split.

  4. In the TC Pairs tab, click Split Pairs.

  5. In the Split Pairs window, ensure that the pair to be split appears in the Selected Pairs table.

  6. For Secondary Volume Write, specify whether the host can write to the S-VOL while the pair is split.

    • Enable accepts host read and write I/Os to the S-VOL. Note the following:

      - If you plan to resynchronize the pair after the S-VOL has been written to while split, you must select Depends on Primary Volume Fence Level for the Primary Volume Write option, below. This ensures that P-VOL and S-VOL bitmaps are merged when the pair is resynchronized.

      - If you specify Enable for this option, and also need the P-VOL to continue accepting host I/O, make sure to select Depends on Primary Volume Fence Level for Primary Volume Write.

      Enable is only available when performing the split operation from the pair's primary storage system.

    • Disable (default) causes the host read and write I/Os to be rejected by the S-VOL while the pair is split.
  7. For Primary Volume Write, specify whether writing to the P-VOL is enabled while the pair is split.

    • Depends on Primary Volume Fence Level: Writing to the P-VOL is based on fence level specified during the Create Pairs operation. This is the default.
    • Disable: Write I/Os to the P-VOL are rejected regardless of the fence level. Select this option to maintain synchronization of the P-VOL and S-VOL. Do not select this option if the P-VOL is necessary for host system operations.

      Disable is only available when performing the split operation from the pair's primary storage system.

    NoteWhen the pair must be split and its P-VOL is required for system operations, you must select Depends on Primary Volume Fence Level, so that the P-VOL continues to accept I/Os.
  8. Click Finish.

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

  10. Click Apply to save your settings.

    After the pair is split, make sure that the TrueCopy pair is displayed correctly (in the PSUS status) in the Remote Replication window.

    To check the pair split operation status, click the update button at the upper right corner of the Device Manager - Storage Navigator main window to update the information in the Remote Replication window, or view the detailed status information in the View Pair Properties (Remote) window.

Resynchronizing pairs

You resynchronize TrueCopy pairs when you recover data from a disaster or when you perform tasks on TrueCopy pairs, like assigning pairs to consistency groups.

While a TrueCopy pair is split, the primary system does not perform update copy operations to the S-VOL. Resynchronizing the pair updates the S-VOL with differential data accumulated since the split, so that its data is again identical with the P-VOL's data. Update copy operations begin again to the S-VOL.

When resynchronizing, TrueCopy pairs can be migrated to global-active device. For details, see the Global-Active Device User Guide.

Before you begin

  • Required role: Storage Administrator (Remote Copy)
  • Required status: Both volumes must be suspended (PSUS or PSUE).
  • This operation is performed from the primary system only.

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, click the TC Pairs tab, and then select the pair to be resynchronized.

  4. In the TC Pairs tab, click Resync Pairs.

  5. In the Resync Pairs window, ensure that the pair to be resynchronized appears in the Selected Pairs table.

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

    • Status: The P-VOL cannot be written to only if the primary system is not able to change S-VOL status to Suspend.
    • Never: The P-VOL can always be written to.
    • Data: The P-VOL cannot be written to when the update copy fails.

    For more information, see Allowing I/O to the P-VOL after a split: Fence Level options.

  7. 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). This option affects performance as follows:

    • For OPEN-V, to change the copy pace, enter a number from 1 to 4.
    • 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.
    • (VSP 5000 series) Other than OPEN-V, to change the copy pace value, 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.
  8. For Copy Priority, enter the priority, or scheduling order, for the resync operation. You can set priority from 1 to 256. The default is 32. For details about priority, see Initial copy priority option and scheduling order.

  9. Click Finish.

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

  11. Click Apply to save your settings.

    After the pair is resynchronized, make sure that the TrueCopy pair is displayed correctly (in the PAIR status) in the Remote Replication window.

    To check the pair resynchronization operation status, click the update button at the upper right corner of the Device Manager - Storage Navigator main window to update the information in the Remote Replication window, or view the detailed status information in the View Pair Properties window.

Deleting pairs

You delete a TrueCopy pair when you no longer need an up-to-date remote copy of the data or if you are recovering data from a disaster.

Deleting a TrueCopy pair deletes the TC relationship, but not the volumes or their data. The following happens when you delete a TrueCopy pair:

  • When it is no longer necessary to maintain a remote copy of the P-VOL, delete a pair from the primary system only. All update operations are stopped and pair status for both the P-VOL and S-VOL changes to unpaired.

    When a pair is deleted, the primary system continues to accept write I/O to the former P-VOL but does not keep track of the updates.

  • Delete a pair from the secondary system only for disaster recovery purposes. When you do this, the secondary system changes the S-VOL pair status to unpaired, the primary system detects that the S-VOL status is unpaired and then changes the P-VOL status to PSUS (Delete pair to RCU).

    To restart a pair that was deleted from the secondary system, you must delete the pair from the primary system and then create the pair from the primary system.

NoteWhen you delete a pair from the secondary system, make sure that the S-VOL and P-VOL are identical, including the volume labels. Take all necessary steps to prevent system problems due to duplicate volumes.

Before you begin

  • Required role: Storage Administrator (Remote Copy)

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, click the TC Pairs tab, and then select the pair or pairs to be deleted.

  4. In the Delete Pairs window, ensure that the pairs to be deleted appear in the Selected Pairs table.

  5. For Delete Mode, specify one of the following:

    • Normal: Deletes the pair only if the primary system can change both P-VOL and S-VOL to unpaired volumes.
    • Force: Forcibly deletes pairs even when the primary system cannot communicate with the secondary system.

      Releases the host waiting for the I/O completion signal from the local storage system which cannot communicate with the remote storage system, and then allows host operations to continue.

  6. Click Finish.

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

  8. Click Apply to save your settings.

    After the pair is deleted, make sure that the TrueCopy pair is not displayed in the Remote Replication window.

    To check the pair deletion operation status, click the update button at the upper right corner of the Device Manager - Storage Navigator main window to update the information in the Remote Replication window, or view the detailed status information in the View Pair Properties (Remote) window.