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Array. Two or more hard
disk drives grouped together to appear as a single device to the
host computer.
Bootable Array Support.
The ability to make the system boot from a RAID array instead of
from a standalone (single) disk.
Cache. A
temporary, fast storage area that holds data from a slower
storage device for quick access. Cache storage is normally
transparent to the accessing device.
Co-processor. A
processor that resides on an array that relieves the host CPU
from executing processor-intensive operations such as RAID 5
parity calculations and secondary RAID 1 writes.
Duplexing.
Mirroring across two RAID cards.
Dynamic Array Expansion.
See "Online Capacity Expansion"
Fault Tolerance. The
ability of a system to continue to perform its functions even
when one or more hard disk drives have failed.
Hot Spare.
A spare hard
drive which will automatically be used to replace the failed
member of a redundant disk array.
Hot Swap. The ability to
remove a failed member of a redundant disk array and replace it
with a good drive without bringing down the server or
interrupting transactions that involve other devices.
Microprocessor. A
processor on the RAID card which performs all RAID management
functions (for example, the Intel i960). Microprocessors offer
higher performance compared to co-processors.
Mirroring (RAID 1).
Provides data protection by duplicating all data from a primary
drive on a secondary drive.
NOS. Network Operating
System (i.e., NetWare, Windows NT server)
Online Capacity Expansion (O.C.E.).
A process for adding storage capacity to an existing RAID array
without having to take the server offline. Also known as Dynamic
Array Expansion.
Parity. A form of data
protection used by RAID level 5 to recreate the data of a failed
drive in a disk array.
RAID Levels. Numbered 0
through 5, RAID levels refer to different array architectures
that offer various advantages in terms of data availability,
cost and performance. RAID levels 0, 1, 0/1, and 5 are the most
popular.
RAID 0. See
"Striping"
RAID 0/1. Combines RAID
0 (data striping) and RAID 1 (disk mirroring).
RAID 1. See
"Mirroring"
RAID 5. Combines data
striping (for enhanced performance) with distributed parity (for
data protection) to provide a recovery path in case of failure.
RAID Management Software.
Software that makes installation, configuration, and management
of RAID arrays easy. Often includes features such as pager
notification and remote management.
SCSI. Stands for Small
Computer System Interface. SCSI is the technology that allows
you to connect various devices to your PC. This connection is
made using a SCSI card that fits inside your computer.
Striping (RAID 0).
Spreads data evenly over multiple drives to enhance performance.
Because there is no redundancy scheme, it does not provide data
protection.
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