Raid 5 Logical Drives - Adaptec CDP-00278-02-A 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, 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.
Disk Drive 1 250 GB
Disk Drive 2 250 GB
Disk Drive 3 400 GB
Disk Drive 4 400 GB
Disk Drives in Logical Drive
Proprietary and Confidential to PMC-Sierra, Inc.
Document No.: CDP-00278-02-A Rev. A, Issue:
Drive Segment Size
(Smallest Disk Drive)
1 4 . . .
Disk Drive 1
2 5 . . .
Disk Drive 2
3 P . . .
Disk Drive 3
P 6 . . .
Disk Drive 4
RAID 5 Logical Drive = 750 GB plus Parity
maxView Storage Manager User's Guide
P
748
749
Unused Space = 150 GB
750
Unused Space = 150 GB
119