Silicon Graphics InfiniteStorage 4000 Series, Configuring And Maintaining

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Chapter 3: Configuration Concepts 45
Volumes A volume is the logical component that hosts use for data storage. Hosts that are
attached to the storage array write data to the volumes and read data from the
volumes. You can create a volume from either a volume group or a disk pool. Before
you create a volume, the volume group or a disk pool must already exist and it must
have enough free capacity to create the volume.
NOTE
Disk pools are available only on the E2600 controller and the E5400 controller.
Table 7 Volume Properties Set Using CLI Commands
A volume is a contiguous subsection of a volume group or disk pool that is configured
to meet application needs for data availability and I/O performance. The storage
management software administers a volume as if the volume is one “drive” for data
storage. Volumes are identified by names or labels that users choose. The volume
names can be any combination of alphanumeric characters, hyphens (-), and
underscores (_). The maximum length of a volume name is 30 characters.
The script commands support the following types of volumes:
 Standard volume
– A logical structure that is the principal type of volume for
data storage. A standard volume is the most common type of volume in a storage
array.

Thin volume
– A logical structure in which the volumes have small physical
storage allocations, but a large virtual capacity available for host I/O data writes.
When you configure a thin volume, you specify two types of capacity: the
virtual
capacity and the
repository
capacity. The virtual capacity is the capacity that is
reported to the host. The repository capacity is the amount of physical drive space
that is currently allocated for writing data.
Properties of a Standard
Volume
Description
Segment size The amount of data stored on a drive before the storage array
moves to the next drive in the stripe (RAID group). Applies only
to volumes in volume groups, not disk pools.
Capacity The amount of data that you can store in a volume.
Controller ownership Defines the controller that is designated to be the owning, or
primary, controller of the volume. Controller ownership is very
important and should be planned carefully. Make sure that the
controllers are balanced as closely as possible for total I/Os.
Mapping How host LUNs are mapped to a volume.
Name Descriptive name indicating the type of data stored in the
volume.