Dell PowerEdge 7150 - Manual (Page 31)

Abbreviation for pin grid array, a type of microprocessor socket that allows you to remove the microprocessor chip.
pixel
Arranged in rows and columns, a pixel is a single point on a video display. Video resolution—640 x 480, for example—is expressed as the number of pixels across by
the number of pixels up and down.
POST
Acronym for power-on self-test. Before the operating system loads when you turn on your system, the POST tests various system components such as RAM, the disk
drives, and the keyboard.
ppm
Abbreviation for pages per minute.
program diskette set
The set of diskettes from which you can perform a complete installation of an application program. When you reconfigure a program, you often need its program
diskette set.
RAID
Acronym for redundant arrays of independent disks. This phrase was introduced by David Patterson, Garth Gibson, and Randy Katz at the University of California at
Berkeley in 1987. The goal of RAID is to use multiple small, inexpensive disk drives to provide high storage capacity and performance while maintaining or improving
the reliability of the disk subsystem.
Patterson, Gibson, and Katz described five different methods, which are known as RAID levels 1 through 5. Each level uses one or more extra drives to provide a
means of recovering data lost when a disk fails, so that the effective failure rate of the whole disk subsystem becomes very low.
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 controller cards are duplexed. See also striping.
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 mirroring, RAID 10, striping.
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 guarding and striping.
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 guarding.
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 mirroring, RAID 1, and
striping.
RAM
Acronym for random-access memory. The system's primary temporary storage area for program instructions and data. Each location in RAM is identified by a number
called a memory address. Any information stored in RAM is lost when you turn off your system.
RCA
Acronym for Resource Configuration Add-in.
RCU
Acronym for Resource Configuration Utility.
read-only file