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

2.4
3PAR Storage Concepts and Terminology
3PAR InForm OS Concepts Guide InForm OS Version 2.3.1
2.1.1 Physical Disks
A physical disk is a hard drive mounted on a drive magazine located in a 3PAR InServ Storage
Server drive cage. For more information about physical disks and the 3PAR InServ Storage
Server hardware platforms, see Chapter 13, 3PAR InServ Storage Server Hardware.
2.1.2 Chunklets
Physical disks are divided into chunklets. Each chunklet occupies 256 MB of contiguous space
on a physical disk. Chunklets are automatically created by the 3PAR InForm
®
Operating System
and they are used to create logical disks. A chunklet is assigned to only one logical disk. For
more information about chunklets, see Chapter 7, Chunklets.
2.1.3 Logical Disks
A logical disk is a collection of physical disk chunklets arranged as rows of RAID sets. Each RAID
set is made up of chunklets from different physical disks. Logical disks are pooled together in
Common Provisioning Groups (CPGs) which allocate space to virtual volumes. The underlying
logical disks are automatically created by the InForm OS when you create CPGs. The RAID type,
space allocation, growth increments and other logical disk parameters can be set when you
create a CPG or modified later. 3PAR storage servers support the following RAID types:
■ RAID 0
■ RAID 10 (RAID 1)
■ RAID 50 (RAID 5)
■ RAID Multi-Parity (MP) or RAID 6
For a detailed discussion of logical disks and RAID types, see Chapter 8, Logical Disks.
2.1.4 Common Provisioning Groups
A Common Provisioning Group (CPG) is a virtual pool of logical disks that allocates space to
virtual volumes on demand. A CPG allows up to 4,095 virtual volumes to share the CPG's
resources. You can create fully-provisioned virtual volumes and Thinly-Provisioned Virtual
Volumes (TPVVs) that draw space from a CPG's logical disk pool. For more information about
CPGs, see Chapter 9, Common Provisioning Groups.