Dell PowerVault LTO4-120 Performance Considerations for Tape Drives and Librar - Page 11
increases. With the larger disk arrays, read performance can actually outperform RAID 0 arrays
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RAID 5 With a RAID 5 array, data is striped across the disk array at the byte level and error correction data, or parity data, is also striped across the disk array. RAID 5 arrays tend to have very good random read performance; this read performance generally improves as the number of disks in the array increases. With the larger disk arrays, read performance can actually outperform RAID 0 arrays because the data is distributed over an additional drive. In additional, parity information is not required during normal reads. Restores from tape to a RAID 5 array tend to be nominal because it involves additional overhead for calculating and writing the parity information. Figure 1-4. Example RAID 5 Configuration Hard Drive 1 Hard Drive 2 Hard Drive 3 Hard Drive 4 P = Parity Byte D = Data Byte P1 D1 D2 D3 D4 P2 D5 D6 D7 D8 P3 D9 D10 D11 D12 P4 D13 D14 D15 D16 Read/Write SCSI or RAID Controller Read/Write Tape Drive Performance Considerations for Tape Drives and Libraries 11