HP LUN Configuration Manager XP Software - Manual (Page 15)

Introduction 15
Important terms and concepts
You should be familiar with the following terms and concepts:
• controller
The disk array has one controller which controls data access and
storage operations. The disk array controller supports OPEN-
x
emulation modes.
• CU (control unit)
Each CU controls up to 256 LDEVs (XP256) or 512 LDEVs (XP512).
The CUs are numbered sequentially from 0 to E.
• LDEV (logical device)
An LDEV results when a RAID group is divided into parts according
to the emulation mode selection (OPEN-
x ). The number of resulting
LDEVs depends upon the selected emulation mode.
• parity group
A parity group is a set of hard disk drives that have the same capacity
and are treated as one group. For example, a parity group of 18-GB
disk drives in a RAID5 configuration consists of four disk drives
(three data and one parity).
• volume
An LDEV can also be called a volume. The LDEV ID is internal to the
disk array and is not related to the volume serial number (volser) or
LUN number.
• path
A SCSI or Fibre Channel port ID, a SCSI target ID (TID), and a LUN
number.