Raid 4, Raid 5, Raid 1 – Dell PowerEdge 6400 User Manual
Page 25: Raid 10
RAID 0
RAID 0 is commonly called striping. This was not originally defined as a RAID level but has since come into popular use. In this array configuration,
data is written sequentially across the available disks and no redundancy is provided. RAID 0 configurations provide very high performance but
relatively low reliability. RAID 0 is the best choice when DSA controller cards are duplexed. See also
RAID 1
RAID 1 is commonly called mirroring. RAID 1 also uses striping, so RAID 1 may be regarded as the mirroring of RAID 0 configurations. RAID 1 is
the best choice in high-availability applications that require high performance or relatively low data capacity. See also
RAID 4
RAID 4 is commonly called guarding. It uses data striping, like RAID 0, but adds a single, dedicated parity drive. The parity data stored on this
drive can be used to recover data lost from a single failed drive. RAID 4 configurations write data slowly because parity data has to be generated
and written to the parity drive, and the generation of the parity data frequently requires reading data from multiple physical drives. See also
.
RAID 5
RAID 5, like RAID 4, is commonly called guarding. RAID 5 is identical to RAID 4, except that the parity data is distributed evenly across all physical
drives instead of a parity drive. In configurations using a large number of physical drives in which a large number of simultaneous small write
operations are being performed, RAID 5 offers potentially higher performance than RAID 4. RAID 4 and RAID 5 configurations are appropriate in
high-availability applications where performance is less critical or where high data capacity is required. See also
RAID 10
RAID 10 is a mirroring technique in which data is duplicated across two identical RAID 0 arrays or hard-disk drives. All data on a physical drive in
one array is duplicated, or mirrored, on a drive in the second array. Mirroring offers complete redundancy of data for greater data security. See
also
,
RAMDAC
random-access memory digital-to-analog converter
read-only file
A read-only file is one that you are prohibited from editing or deleting. A file can have read-only status if:
l
Its read-only attribute is enabled.
l
It resides on a physically write-protected diskette.
l
It is located on a network in a directory to which the system administrator has assigned read-only rights to you.
real mode
An operating mode supported by 80286 or higher microprocessors, real mode imitates the architecture of an 8086 microprocessor. Designed to
run in real mode, MS-DOS (unassisted by additional software techniques) can address only 640 KB of conventional memory.
refresh rate
The frequency, measured in Hz, at which the screen's horizontal lines are recharged. A monitor's refresh rate is also referred to as its vertical
frequency.
REN
ringer equivalence number
RFI
radio frequency interference
RGB
red/green/blue
ROM
Read-only memory. Your computer contains some programs essential to its operation in ROM code. Unlike RAM, a ROM chip retains its contents
even after you turn off your computer. Examples of code in ROM include the program that initiates your computer's boot routine and the POST.
rpm
revolutions per minute