Avago Technologies AcceleRAID 170LP - Manual (Page 74)

G-16 AcceleRAID 170LP Installation Guide
Logical Drive
The logical devices presented to the operating system. System drives are
presented as available disk drives, each with a capacity specified by the
Mylex RAID controller.
Logical Drive States
A logical (system) drive can be Online, Critical, or Offline. Notice that the
term “online” is used for both physical and logical drives. See also Storage
Device.
LUN
Logical Unit Number, a SCSI representation of a system drive on a given
channel and target ID. This may be a single device or an array of devices
configured to behave as a single device.
LVD
Low Voltage Differential, a form of SCSI signaling introduced with Ultra2
SCSI (Fast 40 SCSI). LVD uses data high and data low signal lines to
increase transmission distances over those of single-ended (conventional
SCSI signaling) lines. LVD allows for cable lengths of up to 12 meters
(approximately 39 feet) with up to 15 drives. LVD also lowers noise, power
usage, and amplitude.
LVD differs from conventional differential signaling in that only positive and
negative values are distinguished, not voltage levels. Other advantages are
that LVD devices consume less power and can sense single-ended devices on
the bus and revert to single-ended signaling. Devices need to be Ultra2 SCSI
LVD drives in order to take advantage of the LVD signaling. Mylex
AcceleRAID, eXtremeRAID, and DAC FL controllers are LVD controllers.
Megabit
A million bits; used as a common unit of measure, relative to time in
seconds, as an expression of a transmission technology's bandwidth or data
transfer rates (abbreviated as Mb). Megabits per second (Mbps) is a frequent
measure of bandwidth on a transmission medium.