Definitions for logical storage terms

Article:HOWTO39443  |  Created: 2011-01-06  |  Updated: 2011-01-06  |  Article URL http://www.symantec.com/docs/HOWTO39443
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Definitions for logical storage terms

Logical storage is configured physical storage.

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

Note:

The following terms appear in the Online Storage Capacity Summary report.

See Online Storage Capacity Summary report.

Table: Logical storage terms

Term

Definition

LUN storage

The amount of configured array storage that is 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 amount 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 are not counted as allocated if CommandCentral Storage also discovers the virtualization array.

In 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 the 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 the 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 array and unified device storage 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 the 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 the 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 from the EMC CLARiiON storage arrays that are marked as spare. Examples include:

  • For EMC CLARiiON arrays: PSM, snapshot cache, MirrorView, and hot spares (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 Target

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).

NAS used (NFS SP)

The amount of NAS storage that is given to NFS-based VMware storage pools.

NAS used (Non-NFS SP)

The amount of NAS storage that is given to non-NFS-based VMware storage pools.

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 the additional storage that CommandCentral Storage does not discover. Such additional storage can include disk-format capacity and internal configuration capacity for the array.

For NAS and Unified storage devices, Overhead includes the amount of the storage that is spent during file system creation. This overhead is approximately 1.5 to 2% of the entire production file system. The Overhead data includes things such as the cylinder groups, inodes, and superblock. Also, for NAS and Unified storage devices, (NetApp), Overhead includes RAID overhead.

Snapshot reserve

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

WAFL spares

For NetApp unified storage devices, the amount of storage that is devoted to the file system. This amount is the spare capacity used in the NetApp file system.

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

Unknown

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

For configured thin provisioning arrays, this total also includes storage of disabled source LUNs, and LUNs that are not associated with any thin pool.

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 configured storage that is not apportioned into addressable units (LUNs). This amount can also be configured storage NetApp file systems do not use.

See Definitions for physical storage terms

See Definitions for allocated storage terms

See Definitions for thin provisioning terms

See Definitions for storage consumption terms

See Definitions for storage usage by hosts terms

See Definitions for storage usage by applications terms

See Definitions for virtualization server allocation terms

See Definitions for virtualization server consumption terms

See Definitions for virtualization server usage terms

See Definitions for virtual machine consumption terms

See Definitions for virtual machine usage terms

See Definitions for virtual machine application usage terms


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