Dell Serial Attached SCSI 5iR Integrated and Adapter - Manual (Page 13)

Overview 11
Integrated Mirroring
With Integrated Mirroring (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 Integrated Mirroring is that it provides 100 percent 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 physical disk can act as the
operational physical disk.
NOTE: Mirrored physical disks improve read performance by read load balance.
Figure 1-3. Example of Integrated Mirroring (RAID 1)
Stripe element 1
Stripe element 2
Stripe element 3 Stripe element 1 Duplicated
Stripe element 2 Duplicated
Stripe element 3 Duplicated
Stripe element 4 Stripe element 4 Duplicated
YD912bk1.book Page 11 Monday, April 2, 2007 4:39 PM