Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

Note: If the system crashes during relayout or conversion, the process continues
when the system is rebooted. However, if the system crashes during the first stage
of a two-stage relayout and conversion, only the first stage finishes. To complete
the operation, you must run vxassist convert manually.
Using Thin Provisioning
This section describes how to use VxVM volumes with Thin Storage LUNs.
About Thin Provisioning
Thin Provisioning is a storage array feature that increases storage use by
automating storage provisioning. Administrators do not have to estimate how
much storage an application requires. Instead, Thin Provisioning lets
administrators provision a large Thin LUN to a host. Application I/O writes drive
actual physical capacity allocation on the Thin LUN.
About Thin Reclamation
When data is deleted on a host, nothing happens on a Thin Storage LUN. As a
result, a host writing 200 GB of data on a file system that is supported by a Thin
LUN triggers allocation of at least 200 GB of physical disk space behind the Thin
LUN. If the host subsequently deletes 200 GB of data from that same file system,
the amount of physical storage behind the Thin LUN does not change. In such a
case, there is at least 200 GB of physical disk space behind the Thin LUN, now
unused.
The Storage Foundation Thin Reclamation feature leverages Veritas File System
(VxFS) knowledge of used and unused block ranges at the file system level. It also
lets an administrator trigger online reclamation of unused Thin Storage in storage
arrays that support Thin Reclamation. Thin Reclamation can be triggered on a
file system, a set of disks, a disk group, or an enclosure. It releases unused Thin
Storage to the free storage pool in the array. The Storage Foundation Hardware
Compatibility List lists the storage arrays that support this Thin Reclamation.
Thin Reclamation of a disk, a disk group, or an enclosure
Use the vxdisk reclaim command to trigger online Thin Reclamation on one or
more disks, disk groups, or enclosures. The following example triggers reclamation
on LUNs disk1 and disk2:
# vxdisk reclaim disk1 disk2
Administering volumes
Using Thin Provisioning
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