Acer PCI to Ultra SCSI RAID Controllers DAC960PG Bedienungsanleitung PDF herunterladen (Seite 69)

Glossary

Manual No. 775012 G-11

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.

LVD

Low Voltage Differential, a form of SCSI signaling introduced with Ultra2

SCSI (Fast40 SCSI) 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 devices. 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 devices 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. Megabits per second (Mbps) is a frequent measure of

bandwidth on a transmission medium.

Megabyte

(1,048,576) bytes. One megabyte can store more that one million

characters. Abbreviated as M or MB.

Mirrored Cache

A cache memory that has duplicate data from another controller. In the event

of failure of the original controller, the second controller can take the cached

data and place it on the disk array.

Mirrored Hard Drive

Two hard drives the computer sees as one unit. Information is stored

simultaneously on each drive. If one hard disk drive fails, the other contains

all of the cached data and the system can continue operating.

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Acer PCI to Ultra SCSI RAID Controllers DAC960PG Bedienungsanleitung Seite 69