Dell
RAID 0
RAID 5
RAID 5
Parity | Data 1 | Data 2 | 0 parity | Data 3 | Data 4 | 0 parity | Parity |
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Generation | Data 5 | 1 parity | Data 6 | Data 7 | 1 parity | Data 8 | Generation |
| 2 parity | Data9 | Data 10 | 2 parity | Data 11 | Data 12 |
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| Drive 1 | Drive 2 | Drive 3 | Drive 4 | Drive 5 | Drive 6 |
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Figure 9. Example of RAID 50 (5 + 0)
Advantages of RAID 50
∙Allows creation of largest RAID groups, up to 256 drives (theoretical; large RAID volumes are allowed for up to 192 drives connected to PERC H800)
∙High read transaction rate
∙Higher degree of fault tolerance due to parity calculation being done for each RAID 5 subset
∙Potential for faster read transaction rates over large RAID 5 virtual disks
∙
Disadvantages of RAID 50
∙Disk failure has a medium impact on throughput
∙One of the more complex RAID implementations
∙Less space efficient than RAID 5 since separate parity calculations are done for each RAID 5 subset
∙Retrieval of parity information after a drive failure takes longer than using a mirrored solution
5.3.7RAID 60 (Striping Across RAID 6)
RAID 60 is striping over more than one span of physical disks that are configured as a RAID 6. The RAID 6 subset must have at least four disks. For example, a RAID 6 disk group that is implemented with four physical disks and then continues on with a disk group of four more physical disks would be a RAID 60. See Figure 10.
RAID 60 stripes data across each RAID 6 subset. RAID 60 provides a higher degree of fault tolerance since 2 drives per RAID 6 set may fail without data being lost. A performance increase over RAID 6 may be realized depending on the configuration due to fewer disks reads per parity calculation.
For example, if a comparison of a RAID 6 virtual disk with 8 disks were made to a RAID 60 virtual disk with two 4 disk RAID 6 virtual disks, the parity calculation on the RAID 10 virtual disk would require reading all 6 disks each time, where the parity calculation on the RAID 60 may require only reading 4. This may vary depending on several factors such as cache and data block sizes.
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