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Create consistency groups

A consistency group is a collection of base volumes in your storage array. These base volumes, which are the source of a snapshot image, are referred to as member volumes of a consistency group. The purpose of a consistency group is to take simultaneous snapshot images of multiple volumes, thus ensuring crash-consistent (as opposed to application-consistent) copies of a collection of volumes at a particular point in time.

For example, you can create a consistency group if you want to take a synchronized snapshot image of several volumes that are in different volume groups or disk pools in a storage array. Using the consistency group mechanism is ideal for applications that span multiple volumes, for example, a database application that has the logs on one volume and the database on another volume. Each base volume that belongs to a consistency group is referred to as a "member volume." A member volume is either a standard volume in a disk pool or a volume group, or a thin volume in a disk pool.

When you create a consistency group, the storage management software lets you add member volumes during the creation process or create the consistency group with no member volumes. If you want to add member volumes as part of the creation process, you select the desired volumes from the eligible volumes list and select the automatic or manual member repository creation option.



  1. Consistency group
  2. Schedule is associated with the consistency group
  3. Repositories are created for each member volume
  4. Consistency group snapshot image also creates individual snapshot images for each member volume

With the automatic method, the storage management software uses the default values when creating the associated member repository for each member volume you add to the consistency group. When you select the manual snapshot volume repository creation option, you need to select the Add members now option and select the desired volumes from the list of eligible volumes. With the manual method, you also need to understand how to use the Auto-Choose utility, how to use the repository candidate table, how to set the auto-deletion setting, and how to set the repository utilization threshold percentage. The manual method is considered advanced and only those who understand consistency group functions and optimal drive configurations should use this option.

When you add a member volume to a consistency group, the system automatically creates an associated member repository and a snapshot group for the member volume.

Consistency groups have these characteristics:

For more information, refer to the "Managing Consistency Group Operations" topic in the AMW online help.