Dell PowerEdge 1750 - Manual (Page 28)

PS/2
Abbreviation for Personal System/2.
PXE
Acronym for Preboot Execution Environment.
RAC
Acronym for remote access controller.
RAID
Acronym for redundant array of independent disks. An array of multiple independent hard drives that, in varying levels, provide high performance and fault
tolerance.
The following RAID levels provide various mixes of performance, reliability, and cost: Level 0 (striping), Level 1 (mirroring), Level 5 (striping with parity), Level
10 (striping with mirroring) and Level 50 (linked Level 5 arrays).
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 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 mirroring, RAID 10, and striping.
RAID 3
RAID 3 is commonly called guarding. It uses data striping, like RAID 0, but adds a single, dedicated parity drive for redundancy and block-level parallel access.
The parity data stored on this drive can be used to recover data lost from a single failed drive, and the generation of the parity data frequently requires
reading data from multiple physical drives. RAID 3 is generally used in situations that require large sequential I/Os and a high data-transfer rate, such as video
streaming. See guarding and striping.
RAID 4
RAID 4 is commonly called guarding. It uses a single, dedicated parity drive, like RAID 3, but requires reading and writing large blocks of data to one physical
drive at a time. See guarding and striping.
RAID 5
RAID 5 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 guarding.
RAID 10 (RAID 1+0)
RAID 10 is commonly called RAID 1+0. RAID 10 is a multilevel array that combines mirrored drives (RAID 1) with data striping (RAID 0). In a RAID 10
configuration, data is mirrored on two drives and then striped across two or more sets of mirrored drives. RAID 10 offers the data transfer advantages of
striped arrays and the accessibility features of mirrored arrays. System performance during a drive rebuild is also better than parity-based arrays, since data
does not need to be regenerated from parity information, but simply copied from a surviving drive.
RAID 50
Two or more linked RAID 5 arrays. For example, a RAID 5 array that is implemented with three drives and then continues on with three more array drives
would be a RAID 50 array. RAID 50 provides data redundancy through parity. See parity.
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.
RAS
Abbreviation for Remote Access Service. This service allows users running the Windows operating system to remotely access a network from their system
using a modem.
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 or on a diskette in a write-protected drive.
l It is located on a network in a directory to which the system administrator has assigned read-only rights to you.
readme file
A text file included with a software package or hardware product that contains information supplementing or updating the documentation for the software or