Disk Mirroring - LSI MegaRAID SCSI 320-1 RAID Controller Series 520 Hardware Manual

2.3.5.2 Stripe Size
2.3.6

Disk Mirroring

2-6
The stripe size is the length of the interleaved data segments that
MegaRAID SCSI 320-1 writes across multiple drives. MegaRAID SCSI
320-1 supports stripe sizes of 2, 4, 8, 16, 32, 64, or 128 Kbytes.
With disk mirroring (used in RAID 1), data written to one disk drive is
simultaneously written to another disk drive, as shown in
Figure 2.2 Disk Mirroring
MegaRAID Controller
Segment 1
Segment 2 Segment 2 Duplicated
Segment 3 Segment 3 Duplicated
Segment 4
If one disk drive fails, the contents of the other disk drive can be used to
run the system and reconstruct the failed drive. The primary advantage
of disk mirroring is that it provides 100% data redundancy. Since the
contents of the disk drive are completely written to a second drive, it
does not matter if one of the drives fails. Both drives contain the same
data at all times. Either drive can act as the operational drive.
Although disk mirroring provides 100% redundancy, it is expensive
because each drive in the system must be duplicated.
Introduction to RAID
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Segment 1 Duplicated
Segment 4 Duplicated
Figure 2.2.