Volume groups

The concept of a Volume Group was introduced to simplify the management of both point-in-time and remote copy replication for IBM FlashSystems and IBM Spectrum Virtualize-based systems.

A volume group serves as a container for managing a set of related volumes as a single object. Such a configuration ensures consistency across all volumes in the group, based on the policy or action applied to the entire volume group.

The volumes within a volume group are intended to be mutually consistent, meaning that they only make sense as a cohesive group. As a group of thin clones or clones is populated, the responsibility to ensure that the images are mutually consistent falls on the snapshot function. Also, when volumes are added or removed from a group, it is the responsibility of the host applications to maintain the mutual consistency of the volume groups.

The following section outlines the potential policies or solutions that can be applied to a Volume Group on the storage system.

Safeguarded Copy function

One implementation of volume groups is to group volumes to be configured as Safeguarded. Safeguarded copy function is a cyber-resiliency feature that creates immutable copies of data that cannot be changed or manipulated. A Safeguarded volume group describes a set of source volumes that can span different pools and are backed up collectively with the Safeguarded Copy function. Safeguarded snapshots are supported on the system and can be configured with IBM Copy Services Manager.

Snapshot function

Snapshots are the read-only, point-in-time copies of a volume group that are not directly accessible from the hosts. To access the snapshot contents, you can create a clone or thin clone of a volume group snapshot. You can use the command-line interface or management GUI to configure volume groups to use snapshot policies for multiple volumes for consistent management. Snapshots can either be Safeguarded, set to be deleted only after the specified retention time, or non-Safeguarded, allowing deletion at any time.

Policy-Based Replication function

You can use volume groups for policy-based replication. A replication policy is assigned to the entire volume group. As a result, each volume within the group is configured for policy-based replication. The system automatically replicates both the data and the configuration of volumes within the group, according to the values and settings specified in the replication policy. As part of policy-based replication, a recovery volume group is created automatically on the recovery system. Recovery volume groups cannot be created, changed, or deleted. A single replication policy can be assigned to multiple volume groups to simplify replication management. When more volumes are added to the group, replication is automatically configured for these new volumes. Policy-based replication supports configuration changes while the partnership is disconnected. After the partnership is reconnected, the system automatically reconfigures the recovery system.