Step 2: Select the primary volume

Select the primary volume that you want to use in the mirror relationship and allocate its reserved capacity.

When you select a primary volume on the local 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.

Any volumes you add to the mirror consistency group on the local storage array will hold the primary role in the mirror relationship.

  1. From the list of eligible volumes, select a volume that you want to use as the primary volume, and then click Next to allocate the reserved capacity.
  2. From the list of eligible candidates, select reserved capacity for the primary volume.
    Keep the following guidelines in mind:
    • The default setting for reserved capacity is 20% of the capacity of the base volume, and usually this capacity is sufficient. If you change the percentage, click Refresh Candidates.
    • 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.