Compaq dc7800 - Convertible Minitower PC User Manual page 9

Table 4 RAID 5 with 3 hard drives (Parity)
First Disk
Data Segment 1
Data Segment 3
Parity for 5 and 6
Data Segment 7
Data Segment 9
Parity for 11 and 12
Data Segment 13
Data Segment 15
Parity for 17 and 18
In the previous table, each "Data Segment x" represents a strip. A stripe is made with strip "Data Segment
x", "Data Segment y" and strip "Parity for x and y." Notice that the strip "Parity for x and y" is used to
store the required information to recreate the data if any one of the RAID volume members is compro-
mised.
To better illustrate the concept of RAID 5 (parity based RAID), the following figure shows how a sequence
of data "ABCD..." is stored in a RAID 5. In this example, each letter represents a segment or strip. The fig-
ure shows how the various pieces of the information go to different hard drives, hence if any one member
of the RAID 5 fails, the information from all members is not lost.
Figure 4 RAID 5 with three hard drives
Second Disk
Data Segment 2
Parity for 3 and 4
Data Segment 5
Data Segment 8
Parity for 9 and 10
Data Segment 11
Data Segment 14
Parity for 15 and 16
Data Segment 17
Third Disk
Parity for 1 and 2
Data Segment 4
Data Segment 6
Parity for 7 and 8
Data Segment 10
Data Segment 12
Parity for 13 and 14
Data Segment 16
Data Segment 18
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