3PAR InForm® OS 2.2.4 Concepts Guide (320-200085 Rev B, March 2009)

15.2

Reclaiming Space

3PAR InForm OS Concepts Guide InForm OS Version 2.2.4

All types of volumes are created by mapping data from one or more logical disks to the virtual

volume. Mapping is the correspondence of logical disk regions to virtual volume regions.

Figure 15-1 shows data mapped in regions from logical disks onto a base volume.

Figure 15-1. Data is mapped from logical disks onto a virtual volume in regions

Logical disks can be shared by multiple virtual volumes. Over time, as volumes are deleted or as

volume copy space grows and then shrinks, logical disks can become less efficient in terms of

space.

When logical disks become less efficient in their use of space, they contain unused space that

consumes regions on the LD that is not available for use by the system in creating new logical

disks. Space management commands enable you to consolidate used space onto fewer fully-

utilized logical disks so that unused regions are forced onto one or more logical disks that are

then deleted. Deleting these logical disks frees the unused space for general use by the system.

You can also truncate LDs to free up space. The LD’s used regions are compacted by moving

them to the beginning of the LD and then the LD is shortened so that unused space can be

returned to the system’s free chunklet pool.

There are two general cases where space management commands are useful for reclaiming

unused space on the system:

■ Reclaiming volume space.

■ Reclaiming CPG space.

P (E,F)

P (A,B)

P (G,H)

P (C,D)

AA BBCCDDEE FF A B C D E F

Region

Logical disk (RAID 5)

Virtual volume

Region

Logical disk (RAID 1)

RAID set

Region

Chunklet

Mirror

Region