3PAR InForm® OS 2.3.1 Concepts Guide (320-200112 Rev B, February 2010)

10.3
Virtual Volume Types
InForm OS Version 2.3.1 3PAR InForm OS Concepts Guide
■ Administration space, also known as admin space, is the area of the volume that
corresponds to logical disk regions in the CPG that track changes to the volume since the
previous snapshot was created. The administration space contains pointers to copies of user
data in the snapshot space. Administration space is managed by the system, not with the
tools you use to manage user and snapshot space.
You can increase the size of volumes, the amount of user space, and the amount of snapshot
space for volumes as the requirements increase. If the user space and snapshot space use all
available space, the 3PAR Virtual Copy feature’s copy-on-write operation will fail. To avoid
running out of user space, use TPVVs to automatically draw more user space from a CPG. The
InForm OS automatically reclaims unused snapshot from TPVVs and fully-provisioned virtual
volumes and returns the space to the logical disks.
For greater administrative flexibility, you can provision the virtual volume’s user space and
snapshot space from the same or different CPGs. If the virtual volume’s user space and
snapshot space are on a different CPGs, the user space remains available to the host if the CPG
containing the snapshot space becomes full. To save time by not repeating tasks, you can
create many identical virtual volume’s at one time.
10.2.1 Administrative Volumes
As part of installation and setup process, a volume called the administrative volume, or admin
volume, is created on the system. This volume is used by the system to store administrative
data such as the system event log. The admin volume is always named admin. This volume
cannot be exported and cannot be removed from the system.
10.2.2 Fully-Provisioned Virtual Volumes
A fully-provisioned virtual volume is a volume that uses logical disks that belong to a logical
disk pool known as a Common Provisioning Group (CPG). Unlike Thinly-Provisioned Virtual
Volumes (TPVVs), fully-provisioned virtual volumes have a set amount of user space allocated
in the system for user data. They require the system to reserve the entire amount of space
required by the fully-provisioned virtual volume wether or not the space is actually used. The
fully-provisioned virtual volume size is fixed, and the size limit is 16 TB. You can set snapshot
space allocation limits and usage warnings to help manage the growth of snapshot space.
CAUTION: It is strongly recommended that you do not tamper with the admin
volumes.