HP 3PAR StoreServ Concepts Guide: HP 3PAR OS 3.1.3

Reclaiming Unmapped LD Space from Volumes
When multiple identical virtual volumes are created as a result of a single volume creation operation,
the underlying LDs that support those volumes are shared by the volume group. If several of the
members of that volume group are later deleted, the underlying LDs may become less efficient in
the usage of space. One or more LDs shared by the volume group may have only a small portion
of their regions mapped to existing virtual volumes. However, their unused regions are not available
to the system for use in creating new LDs. Compacting the LD regions mapped to these volumes
may recover and free LD space.
You can compact LDs only with the HP 3PAR CLI. See the HP 3PAR Command Line Interface
Administrator’s Manual for instructions on performing this task.
You can use the optional HP 3PAR Dynamic Optimization Software feature to configure volumes
to use space more efficiently. To learn about tuning volumes for optimal performance, see “Enhanced
Storage Applications” (page 54).
Automatically Reclaiming Unused Snapshot Space from Volumes
The HP 3PAR OS automatically reclaims unused snapshot and administration space from TPVVs
and FPVVs and returns the space to the LDs. The system examines the snapshot and administration
space for large areas of unused space. The identified areas are unmapped from the corresponding
LD regions and the space is returned to the LDs.
Manually Reclaiming Unused Snapshot Space from Volumes
You cannot manually remove snapshot and administration space from a TPVV because the HP
3PAR OS automatically removes any unused space.
Reclaiming dormant snapshot and administration space from an FPVV and returning the space to
the LD can only be performed when the volume is not exported to a host, and if there are no
snapshots of the volume. Creating physical copies of the volume does not prevent you from
reclaiming space.
You can reclaim snapshot space from a virtual volume with the HP 3PAR CLI and the HP 3PAR
Management Console. See the HP 3PAR Command Line Interface Administrator’s Manual and the
HP 3PAR Management Console Online Help for instructions on performing this task.
Deleted Volume Snapshot Space
The unused space associated with deleted snapshots of TPVVs and FPVVs is automatically returned
to the pool of LDs used by the CPG.
Logical Disks and Chunklet Initialization
After deleting logical disks, the underlying chunklets must be initialized before their space is
available to build logical disks. The initialization process for chunklets generally takes about one
minute per 1 GB chunklet and 20 seconds per 256 MB chunklet. To see chunklets that are currently
in the process of being initialized, issue the showpd –c command. Chunklets that are uninitialized
are listed in the Uninit column.
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