Logical storage

Physical storage that has been configured is known as logical storage.

Table: Logical storage terms provides a list of logical storage terms.

Table: Logical storage terms

Term

Definition

LUN storage

The amount of configured storage in an array that has been apportioned into LUNs and is ready to be allocated to hosts.

LUN storage is the sum of replication storage, administrative storage, allocated storage, and unallocated storage.

Also referred to as addressable storage.

Allocated storage

The amount of storage that is apportioned into LUNs and designated for use by specific hosts. This includes array LUNs masked to hosts and other LUNs (typically on JBODs, SCSI disks, or IDE disks) claimed by hosts. ("Claimed" means that the operating system has written a device handle for the LUN.)

This value does not include LUNs designated for replication.

LUNs allocated to a virtualization array, such as a TagmaStore, are not counted as allocated if the virtualization array is also discovered by CommandCentral Storage.

In NetApp Unified Storage Systems, allocated storage applies only to storage that is configured for block (FC) mode.

For Hitachi arrays, CommandCentral Storage defines allocated storage differently than HiCommand Device Manager. The difference is as follows:

  • CommandCentral Storage— Allocated storage is storage that is apportioned into LDEVs or LUSEs. The LDEVs or LUSEs are part of one or more host storage domains. Each host storage domain has one or more hosts (HBAs) masked to it.

  • HiCommand Device Manager— Allocated storage is storage that is apportioned into LDEVs or LUSEs. The LDEVs or LUSEs are part of one or more host storage domains. Each host storage domain may or may not have hosts (HBAs) masked to it.

Unallocated storage

The amount of storage in arrays and unified storage devices that is apportioned into LUNs but not designated for use by specific hosts. These are LUNs that have not been masked to a host and LUNs for which no device handles have been written.

This value does not include storage in JBODs, in SCSI disks, or in IDE disks.

This value does not include LUNs designated for replication.

For Hitachi arrays, CommandCentral Storage defines unallocated storage differently than HiCommand Device Manager. The difference is as follows:

  • CommandCentral Storage— Unallocated storage is storage that is apportioned into LDEVs or LUSEs. The LDEVs or LUSEs may or may not be part of a host storage domain. If the LDEVs or LUSEs are part of a host storage domain, the host storage domain does not have any hosts (HBAs) masked to it.

  • HiCommand Device Manager— Unallocated storage is storage that is apportioned into LDEVs or LUSEs. The LDEVs or LUSEs are not part of a host storage domain.

Administrative

LUNs that are designated for administrative uses, not including RAID overhead and luns of EMC Clariion array that are marked as spare. Examples include:

  • For EMC CLARiiON arrays: PSM, snapshot cache, MirrorView, and hot spares (in EMC CLARiiON physical disks cannot be marked as spare, only LUNs can be marked as spare)

  • For EMC Symmetrix and DMX arrays: VCMDB, Symmetrix file system device, and save device

  • For Hitachi arrays managed by HiCommand: OnDemandDevice and CommandDevice

Replication

LUNs that are designated as target LUNs for snapshot or replication techniques. An example is a business continuance volume (BCV) on a Symmetrix or DMX array, which contains a copy of a standard device (STD).

Network attached storage (NAS) used

The amount of unified storage that is being used by file systems or databases using either the NFS or CIFS protocol in file-sharing mode. (NetApp Unified Storage Systems are examples of unified storage devices.) This includes the file system capacity that is used in file-sharing mode.

If the unified storage device is being used purely in block mode, this value will be zero.

Overhead

The amount of configured storage that is reserved for overhead, most commonly for RAID techniques such as mirroring and striping. Depending on the array type, this value can also include additional storage—such as disk-format capacity and internal configuration capacity for the array—that is not discovered by CommandCentral Storage.

Snapshot reserve

For unified storage devices, the amount of storage that is reserved for snapshots in the file system.

RAID overhead

For unified storage devices, the amount of storage that is reserved for RAID techniques such as mirroring and striping.

WAFL spares

For unified storage devices, the amount of storage that is devoted to the file system.

This value is calculated as follows: Physical capacity minus the sum of logical capacity, snapshot reserve, and RAID overhead.

Unknown

Any logical storage for which discovery information is not available to CommandCentral Storage, represented as the total amount of physical configured storage minus the sum of all other logical storage. This value will typically be zero.

Available storage

The amount of configured storage that has not yet been apportioned into addressable units (LUNs). This storage is typically part of raw storage volumes such as RAID groups.

Available storage reflects configured storage in arrays and unified storage devices only. It does not include storage in JBODs, in SCSI disks, or in IDE disks.

Available volume

For unified storage devices, the amount of unused storage in file systems.

Storage pool/RDM

Administrative/Overhead