Dell PowerEdge RAID Controller 6E - Manual (Page 18)

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Overview
For example, in a four-disk system using only disk striping (used in RAID 0),
segment 1 is written to disk 1, segment 2 is written to disk 2, and so on. Disk
striping enhances performance because multiple physical disks are accessed
simultaneously, but disk striping does not provide data redundancy.
Figure 2-1 shows an example of disk striping.
Figure 2-1. Example of Disk Striping (RAID 0)
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 rebuild the failed physical disk. The primary
advantage of disk mirroring is that it provides complete 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 of the physical disks can act as the operational physical disk.
Disk mirroring provides complete redundancy, but is expensive because each
physical disk in the system must be duplicated.
NOTE:
Mirrored physical disks improve read performance by read load balance.
Stripe element 1
Stripe element 5
Stripe element 9 Stripe element 2
Stripe element 6
Stripe element 10 Stripe element 3
Stripe element 7
Stripe element 11 Stripe element 4
Stripe element 8
Stripe element 12
Dell_PERC6.2_UG.book Page 18 Wednesday, June 24, 2009 6:08 PM