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

8.2
Logical Disks and Common Provisioning Groups
3PAR InForm OS Concepts Guide InForm OS Version 2.3.1
allocation, growth increments and other logical disk parameters can be set when you create a
CPG or modified after creating a CPG. For information about CPGs, see Chapter 9, Common
Provisioning Groups.
8.2 Logical Disks and Common Provisioning Groups
Creating a Common Provisioning Group (CPG) establishes a virtual pool of logical disks that can
grow on demand. When you create virtual volumes, the system creates all underlying logical
disks for you automatically. Volumes associated with a CPG draw logical disk space from the
virtual pool as needed, allocating space on demand. As the volumes that draw from a CPG
require additional storage, the system automatically creates additional logical disks and adds
them to the pool. Once you create a CPG, you can add and remove logical disks. You can also
specify advanced logical disk parameters when creating CPGs. This allows you to exercise a
greater degree of control over how the system creates logical disks within the CPG.
8.3 Logical Disk Types
The following logical disk types provide storage space to virtual volumes:
■ User logical disks provide user storage space to virtual volumes. The user space contains the
user data and is exported as a LUN to the host.
■ Snapshot data logical disks provide the storage space for snapshots or virtual copies. The
snapshot space contains copies of user data that changed since the previous snapshot of
the volume was created.
■ Snapshot administration logical disks provide the storage space for snapshot
administration. The administration space is used to track changes to the volume since the
previous snapshot was created.
The system sets aside logical disks for logging, for preserved data, and for system
administration. The following logical disk types are created by the system:
■ logging logical disks are RAID 10 logical disks that are used to temporarily hold data during
disk failures and disk replacement procedures. Logging logical disks are created by the
NOTE: Creating virtual copies or snapshots requires the 3PAR Virtual Copy license.
For more information, see 3PAR InForm Software on page 2.7