HP StorageWorks XP48 - Disk Array, Owner'S Manual

Page: 98 / 124

98 HP SureStore E Disk Array XP512/XP48: Owner’s Guide
Understanding RAID3
RAID3 is not supported on your XP disk array, but it is a preface to
understanding RAID5, which is supported.
RAID3 allows data to be split and distributed on two or more disk drives
using striping. Because two or more disk drives are recording the data
simultaneously, the transfer speed is faster. The multiple disk drives that are
used to store the data are called a parity group. See figure 14 (page 98).
RAID3 stores parity information on a separate drive (called a parity drive).
This improves the safety of your data because the parity information can be
used to recover the data, even if one of the drives in a parity group has
become inoperative or has read errors.
Because RAID3 does not have parallel input/output capability, it must drive
two or more drives at the same time. This causes poor performance in
applications that process small data files often (transaction processing).
RAID3 has good performance when you are using applications that process
large data files in a single run (scientific computations).
Figure 14. RAID3 Disk Array
DATA
A B C D E F. . .
A
A2 A3 A1
Striping
A1
Parity
Generation
Correction Code
RAID Controller
B1
C1
D1
A3
B3
C3
D3
A2
B2
C2
D2
AP1
BP1
CP1
DP1