Introduction to Volumes

In a PS Series group, each volume is assigned a size, storage pool, and access controls. Optionally, you can reserve snapshot or replication space for a volume. Volume data is automatically load balanced across pool members, as needed.

Volumes are seen on the network as iSCSI targets. Only hosts with an iSCSI initiator and the correct access credentials can access a volume. The group automatically generates an iSCSI target name for each volume. This is the name that iSCSI initiators use to access the volume.

An iSCSI target name consists of a prefix (iqn.2001-05.com.equallogic), followed by a generated string, followed by the volume name. An iSCSI target name must always adhere to the iSCSI protocol specification.

An example of an iSCSI target name for a volume named db3 is shown next:

iqn.2001-05.com.equallogic:7-8b0900-6d0000000-001ebbc5d80sf0k0-db3

For backup or disaster recovery purposes, you can create volume snapshots or replicate a volume to a different group. You can also clone a volume, snapshot, or replica to create an exact copy.

Related volumes can be grouped into a volume collection. You can then create snapshots or replicas of the volumes in one operation. In addition, schedules can be set up to create snapshots or replicas of volumes and volume collections at a specific time or on a regular basis.

Optionally, you can use thin provisioning to improve storage resource utilization by logically over-allocating SAN volumes. Thin provisioning enables you to satisfy current and future storage needs and eliminates the difficulty of adding storage to operating systems or applications that do not support online expansion.

A volume has two sizes associated with it. The reported size is the size that is seen by iSCSI initiators. Systems connected to the volume will associate this amount of space with the volume. The volume reserve is the amount of space that is allocated to the volume. For a volume without thin provisioning, the reported size and the volume reserve will be the same. For a thin-provisioned volume, the reported size will be greater than (or equal to) the volume reserve, because the volume is not fully allocated.

See Understanding Thin Provisioning for more information about thin provisioning. See Snapshot Management and Basic Replication for more information about snapshots and replicas.