Instruction Manual

166 Glossary
Non-Volatile Cache
A cache module with flash-based storage to preserve cache data indefinitely.
This replaces the need for a battery backup unit (BBU) to supply power to
preserve cache data.
O
Offline
A physical disk is offline when it is part of a virtual disk but its data is not
accessible to the virtual disk.
Online
An online device is a device that is accessible.
Online Capacity Expansion
Operation to add capacity to an existing virtual disk by adding an additional
physical disk while the host system is active, and without affecting data
availability.
Operating Environment
An operating environment can include the host system where physical disks are
attached, any I/O buses and controllers, the host operating system and any
additional software required to manage the virtual disk.
P
Parity
An extra bit added to a byte or word to reveal errors in storage (in RAM or disk)
or transmission. Parity is used to generate a set of redundancy data from two or
more parent data sets.
Partition
A logical structure on a contiguous segment of storage on a physical disk or
virtual disk recognized by an operating system.
PERC7.2_UG.book Page 166 Thursday, March 3, 2011 2:14 PM