Create asynchronous mirrored volume

You mirror a volume asynchronously to maintain data at the remote storage array to be a point-in-time consistent copy of data at the local storage array. You do this by creating a mirror consistency group to establish the mirroring relationship between the two storage arrays, and then selecting the primary volume and secondary volume that you want to use in the mirror.

Before you begin

About this task

The process to mirror a volume asynchronously is a multi-step procedure:

A volume can participate in only one mirror relationship.

Step 1: Create a mirror consistency group or select an existing one

You create a mirror consistency group or select an existing one to establish the mirroring relationship between the local storage array and the remote storage array.

About this task

The number of mirror consistency group relationships and mirrored pair relationships that you can create depends on the hardware in your storage array.

Procedure

  1. Do one of the following actions to access the asynchronous mirroring sequence:
    • Select Storage > Asynchronous Mirroring > Create Mirrored pair.
    • Select Storage > Volumes > Copy Services > Mirror a volume asynchronously.
  2. Either select an existing mirror consistency group or create a new one.

    To create new mirror consistency group, do the following:

    1. Enter a unique name that best describes the data on the volumes that will be mirrored between the two storage arrays (for example, R&D Data).
    2. Select the remote storage array on which you want to establish a mirror relationship with the local storage array.
      Note: If your remote storage array is password protected, the system prompts for a password.
    3. Choose whether you want to resynchronize the mirrored pairs on the remote storage array either manually or automatically.
      • Manual — You must explicitly update the secondary point-in-time image using the Manual Resynchronization menu option. Select this option to manually start resynchronization for all asynchronous mirrored pairs within the asynchronous mirror group.
      • Automatic — Using the drop-down, specify the time from the beginning of the previous update to the beginning of the next update. To change the automatic synchronization interval from the default of every 10 minutes, edit the interval value, which is defined in minutes.
    4. Click Create.

      System Manager creates the mirror consistency group on the local storage array first and then creates the mirror consistency group on the remote storage array.

      Note: If System Manager successfully creates the mirror consistency group on the local storage array, but fails to create it on the remote storage array, it automatically deletes the mirror consistency group from the local storage array. If an error occurs while System Manager is attempting to delete the mirror consistency group, you must manually delete it.
  3. Select Next and go to Step 2: Select the primary volume.

Step 2: Select the primary volume

You must select the primary volume that you want to use in the mirror relationship and allocate its reserved capacity. Any volumes added to the mirror consistency group on the local storage array will hold the primary role in the mirror relationship.

Procedure

  1. Select an existing volume that you want to use as the primary volume in the mirror, and then click Next to allocate the reserved capacity.
  2. Allocate the reserved capacity for the primary volume you selected. Do one of the following actions:
    • Accept the default settings – Use this recommended option to allocate the reserved capacity for the primary volume with the default settings.
    • Allocate your own reserved capacity settings to meet your data storage needs related to asynchronous mirroring – Allocate the reserved capacity using the following guidelines.
      • The default setting for reserved capacity is 20% of the capacity of the base volume, and usually this capacity is sufficient.
      • The capacity needed varies, depending on the frequency and size of I/O writes to the primary volume and how long you need to keep the capacity.
      • In general, choose a larger capacity for reserved capacity if one or both of these conditions exist:
        • You intend to keep the mirrored pair for a long period of time.
        • A large percentage of data blocks will change on the primary volume due to heavy I/O activity. Use historical performance data or other operating system utilities to help you determine typical I/O activity to the primary volume.
  3. Select Next and go to Step 3: Select the secondary volume.

Step 3: Select the secondary volume

You must select the secondary volume that you want to use in the mirror relationship and allocate its reserved capacity. Any volumes added to the mirror consistency group on the remote storage array will hold the secondary role in the mirror relationship.

About this task

When you select a secondary volume on the remote storage array, the system displays a list of all the eligible volumes for that mirrored pair. Any volumes that are not eligible to be used do not display in that list.

Procedure

  1. Select an existing volume that you want to use as the secondary volume in the mirrored pair, and then click Next to allocate the reserved capacity.
  2. Allocate the reserved capacity for the secondary volume you selected. Do one of the following actions:
    • Accept the default settings – Use this recommended option to allocate the reserved capacity for the secondary volume with the default settings.
    • Allocate your own reserved capacity settings to meet your data storage needs related to asynchronous mirroring – Allocate the reserved capacity using the following guidelines.
      • The default setting for reserved capacity is 20% of the capacity of the base volume, and usually this capacity is sufficient.
      • The capacity needed varies, depending on the frequency and size of I/O writes to the primary volume and how long you need to keep the capacity.
      • In general, choose a larger capacity for reserved capacity if one or both of these conditions exist:
        • You intend to keep the mirrored pair for a long period of time.
        • A large percentage of data blocks will change on the primary volume due to heavy I/O activity. Use historical performance data or other operating system utilities to help you determine typical I/O activity to the primary volume.
  3. Select Finish to complete the asynchronous mirroring sequence.

Result

System Manager performs the following actions:

  • Begins initial synchronization between the local storage array and the remote storage array.
  • If the volume being mirrored is a thin volume, only the provisioned blocks (allocated capacity rather than reported capacity) are transferred to the secondary volume during the initial synchronization. This reduces the amount of data that must be transferred to complete the initial synchronization.
  • Creates the reserved capacity for the mirrored pair on the local storage array and on the remote storage array.