Raid 5 Logical Drives - Adaptec 5445Z User Manual

RAID 5 Logical Drives

A RAID 5 logical drive is built from a minimum of three disk drives, and uses data striping and
parity data to provide redundancy. Parity data provides data protection, and striping improves
performance.
Parity data is an error-correcting redundancy that's used to re-create data if a disk drive fails.
In RAID 5 logical drives, parity data (represented by Ps in the next figure) is striped evenly
across the disk drives with the stored data.
Drive segment size is limited to the size of the smallest disk drive in the logical drive. For
instance, a logical drive with two 250 GB disk drives and two 400 GB disk drives can contain
750 GB of stored data and 250 GB of parity data, as shown in this figure.
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
Disk Drives in Logical Drive
Appendix B: Selecting the Best RAID Level
Drive Segment Size (Smallest Disk Drive)
250 GB
250 GB
Disk Drive 1
Disk Drive 2
400 GB
Disk Drive 3
Disk Drive 4
400 GB
1 4 ... P
2 5 ... 748
3 P ... 749
Unused Space = 150 GB
P 6 ... 750
Unused Space = 150 GB
RAID 5
= 750 GB plus Parity and Spare
Logical Drive
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