Installation guide

G-4 AcceleRAID Installation Guide
Offline: A Logical Drive is in an “offline” state if...
No data can be read from it or written to it.
System commands issued to offline logical drives are returned with an error
status: no operations can be performed on offline logical drives. A logical
drive can be “offline” under one of two situations described below:
• It is configured with a redundant RAID level (1, 3, 5, or 0+1), and two
or more of its SCSI drives are not “online”; or
• It is configured at RAID level 0, JBOD, or in a spanned set, and one or
more of its SCSI drives are not “online.”
Logical Drives
See “System Drives.”
LVD – Low Voltage Differential
Low Voltage Differential is a form of SCSI signalling that was introduced
with Ultra2 SCSI. Low Voltage Differential allows cable lengths of up to 12
meters (approximately 39 feet) with up to 15 devices. The devices need to be
Ultra2 SCSI LVD devices in order to take advantage of the LVD signalling.
LVD uses data high and data low signal lines to increase transmission
distances over those of single-ended (conventional SCSI signalling). LVD
differs from conventional differential signalling. LVDs advantages are that it
consumes less power and it can sense single-ended devices on the bus and
revert to single-ended signalling.
Mirroring
Refers to the 100 percent duplication of data on one disk drive to another
disk drive. Each disk will be the mirror image of the other.
Pack
See “Drive Groups (or Drive Packs).”
Parity
See “Rotated XOR Redundancy.”