Adaptec 6405 Uživatelská příručka stáhnout pdf (Strana 77)

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 gure) 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 gure.

Unused Space = 150 GB

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

250 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

P1 4 . . .

7482 5 . . .

7493 P . . .

750P 6 . . .

77Proprietary and Condential to PMC-Sierra, Inc.

Document No.: CDP-00277-02-A Rev. A, Issue:

Serial Attached SCSI RAID Controllers Installation and User's Guide

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Adaptec 6405 Uživatelská příručka Strana 77