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 disk |
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Data Segment 1 | Data Segment 2 | Parity for 1 and 2 |
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Data Segment 3 | Parity for 3 and 4 | Data Segment 4 |
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Parity for 5 and 6 | Data Segment 5 | Data Segment 6 |
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Data Segment 7 | Data Segment 8 | Parity for 7 and 8 |
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Data Segment 9 | Parity for 9 and 10 | Data Segment 10 |
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Parity for 11 and 12 | Data Segment 11 | Data Segment 12 |
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Data Segment 13 | Data Segment 14 | Parity for 13 and 14 |
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Data Segment 15 | Parity for 15 and 16 | Data Segment 16 |
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Parity for 17 and 18 | Data Segment 17 | Data Segment 18 |
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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 compromised.
To better illustrate the concept of RAID 5
Figure 4: RAID 5 with three hard drives
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