Dell PowerVault 132T LTO/SDLT (Tape Library) - Manual (Page 11)

Performance Considerations for Tape Drives and Libraries
11
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
P1
D4
D7
D10
D13
D1
P2
D8
D11
D14
D2
D5
P3
D12
D15
D3
D6
D9
P4
D16
SCSI or RAID
Controller
Tape Drive
Read/Write
Read/Write
D = Data Byte
Hard Drive 1 Hard Drive 2 Hard Drive 3 Hard Drive 4
P = Parity Byte