B.6
RAID 5 Arrays
A RAID 5 array 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
arrays, 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 array. For instance, an array 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.
Unused Space = 150 GB
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
250 GB
250 GB
400 GB
400 GB
Drive Segment Size
(Smallest Disk Drive)
Disk Drive 2
Disk Drive 3
Disk Drive 4
Disk Drive 1
Unused Space = 150 GB
Disk Drives in Logical Drive
RAID 5 Logical Drive = 750 GB plus Parity
P
1 4
. . .
748
2 5
. . .
749
3 P
. . .
750
P 6
. . .
52
Microsemi Proprietary and Confidential. Installation and User's Guide Revision 5
Understanding RAID
