AHCI and RAID on HP Compaq Elite 8000, 8100, and 8200 Business PCs

Figure 3. Reliability: RAID 1 - Mirroring

RAID 5 with three hard drives

RAID 5 has been used in servers for many years and is one of the most common

types of RAID. RAID 5 uses striping with parity data in distributed blocks across all

member disks. Therefore, the mass storage controller can simultaneously write new

information to two hard drives and parity information to the third hard drive, so if

one hard drive fails, the RAID controller can rebuild all the information after the

volume degradation occurred. Hence, RAID 5 with three hard drives has similar

performance to RAID 0 with two hard drives, and the reliability of RAID 1 with a

minimum of three hard drives.

Table 5. RAID 5 with three hard drives (Parity)

First Disk Second Disk Third Drisk

Data Segment 1 Data Segment 2 Parity for 1 and 2

Data Segment 3 Parity for 3 and 4 Data Segment 4

Parity for 5 and 6 Data Segment 5 Data Segment 6

Data Segment 7 Data Segment 8 Parity for 7 and 8

Data Segment 9 Parity for 9 and 10 Data Segment 10

Parity for 11 and 12 Data Segment 11 Data Segment 12

Data Segment 13 Data Segment 14 Parity for 13 and 14

Data Segment 15 Parity for 15 and 16 Data Segment 16

Parity for 17 and 18 Data Segment 17 Data Segment 18