3PAR InForm® OS 2.2.4 Concepts Guide (320-200085 Rev B, March 2009)

2.2
3PAR Storage Concepts and Terminology
3PAR InForm OS Concepts Guide InForm OS Version 2.2.4
2.1 3PAR Storage Concepts and Terminology
The 3PAR storage system is comprised of the following layers:
■ Physical disks
■ Logical disks
■ Virtual volumes
■ LUNs and VLUNs
2.1.1 Physical Disks
A physical disk is a Fibre Channel or Near Line disk mounted onto a drive magazine in a storage
server drive cage.
There are three models of drive cages: DC2, DC3, and DC4. The InServ S-Class Storage Servers
and T-Class Storage Servers may contain both DC2 and DC4 drive cages. The InServ E-Class
Storage Servers and F-Class Storage Servers only contain DC3 drive cages.
■ The DC2 and DC4 drive cages contain ten drive bays numbered 0 through 9. Each drive bay
accommodates a single drive magazine that holds four disks.
■ The DC3 drive cage contains 16 drive bays at the front, each accommodating the
appropriate plug-in drive carrier module. The 16 drive bays are arranged in four rows of
four drives.
Physical disks are divided into chunklets. Each chunklet occupies 256 MB of contiguous space.
Space on a physical disk is allocated as follows:
■ One chunklet, or 256 MB, starting from disk logical-block address 0, is reserved for the
Table Of Contents (TOC), which contains the internal description of the system. The TOCs
on all physical disks in the system contain the same information.
■ 4 MB are reserved for diagnostic use--2 MB beginning after the TOC and 2 MB from the
end of the disk logical-block address.