Chapter 4
SV-2003-X2 Server
Part Number: 1006446
Page 66 of 72
Version 1.0. 10/30/07
6.1.1 Reasons for RAID
Depending on how you implement RAID (which
RAID level you use), the benefits include one
or both of the following:
•
Faster performance
: In RAID 0, 10, or 50
arrays, the host system can access multiple
disks simultaneously. This improves
performance because each disk in an array
has to handle only part of the request. For
example, in a two-disk array, each disk needs
to provide only its part of the requested data.
•
Data protection
: In RAID 1, 10, 5, and 50
arrays, the data is backed up either on an
identical disk (mirror) or on multiple disks
(parity disks). RAID 10 and 50 also allow the
host to access disks simultaneously.
6.1.2 RAID Level 0
RAID Level 0 is not redundant, hence does not
truly fit the "RAID" acronym. In Level 0, data is
split across drives, resulting in higher data
throughput. Since no redundant information is
stored, performance is very good, but the
failure of any disk in the array results in all data
loss. This level is commonly referred to as
striping.
6.1.3 RAID Level 1
See Figure 6-1 RAID Level 1 is commonly
referred to as mirroring with 2 hard drives. It
provides redundancy by duplicating all data
from one drive on another drive. The
performance of a Level 1 array is slightly better
than a single drive, but if either drive fails, no
data is lost. This is a good entry-level
redundant system, since only two drives are
required. However, since one drive is used to
store a duplicate of the data, the cost per
megabyte is high.
