Dell PS4100 Technical Information download pdf (Page 31)

June 2012 Dell EqualLogic Configuration Guide v13.2 25

Note: IQN names are assigned to volumes automatically when they are created. They cannot be

changed for the life of the volume. If a volume name is changed, the IQN name associated with

the volume will remain unchanged.

3.3.2 Volume Features

Each volume supports a set of features and capabilities that include the following:

• Ability to define a volume as thin-provisioned

• Support for snapshots

• Support for replication

• Support for creating clones

• Support for multiple host shared access

Note: These block level volume features are not applicable to the component volumes created by

the NAS Service for the FS Series NAS Reserve.

3.4 Thin Provisioning

Thin provisioned volumes provide administrators with an additional option for managing data growth

within the SAN. Thin provisioning allows volumes to present a logical capacity to the host(s)

connecting to the volume that is different (larger) than the actual physical storage resource allocation

used by the volume at any given time.

Note: Volumes automatically created and managed by the NAS Service inside the NAS Reserve

pool used by an FS Series appliance are fully allocated at creation and cannot be thin provisioned.

Once those volumes are created (when the NAS Reserve is created they cannot be shrunk.

A volume can be provisioned as a thin provisioned volume at creation or after creation. The following

rules apply to thin provisioned volumes:

• A minimum physical allocation of 10% of the logical allocation is required

• If a volume is converted to a thin provisioned volume, physical allocation cannot be less than

the amount of physical space already used within the volume

• Any pool free space allocated to a thin provisioned volume is not returned to the free pool if

the host’s file system usage of that volume is reduced (due to file system defragmentation,

data removal, etc.)

• If a thin provisioned volume’s allocated space exceeds the “maximum in-use space” setting,

the volume will go into an offline state.

• Converting a volume to a thin provisioned volume may not reduce the physical allocation of

space the volume is using. Actual physical space recovered will depend on previous writing

patterns for the OS file system hosted on the volume.

• All initial settings for “minimum volume reserve”, “In-use volume reserve warning level” and

“maximum in-use space” are default recommendations and can be changed by the

administrator within the constraints defined above.

The following best practices should be considered when using thin provisioned volumes:

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Dell PS4100 Technical Information Page 31