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Disk Mirroring

With mirroring (used in RAID 1), data written to one disk is simultaneously written to another disk. If one disk fails, the contents of the other disk can be used to run the system and reconstruct the failed disk. The primary advantage of disk mirroring is that it provides 100% data redundancy. Because the contents of the disk are completely written to a second disk, it does not matter if one of the disks fails. Both disks contain the same data at all times. Either drive can act as the operational drive.

Disk mirroring provides 100% redundancy, but is expensive because each drive in the system must be duplicated.

F i g u r e 2 - 2 . E xa m pl e o f D i s k M i r r or i n g

Segment 1

Segment 1 Duplicated

Segment 2

Segment 2

Duplicated

Segment 3

Segment 3

Duplicated

Segment 4

Segment 4 Duplicated

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Introduction to RAID

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Dell 3 manual Disk Mirroring, G u r e 2 2 . E xa m pl e o f D i s k M i r r or i n g