User`s guide

StorageWorks RAID Array 200 Controller Installation and Standalone Configuration Utility
1–4 EK–SWRA2–IG. C01
1.1.2.2 RAID 1
RAID 1 writes a segment of data to two drives simultaneously, as shown in
Figure 1–2. This is the simplest way to achieve data redundancy, known as
mirroring. If one drive fails the controller can retrieve the data from the other
drive in that set.
The cost of data storage is greater than for a single drive, since double the disk
space is required. However, RAID 1 is a consideration for users where reliability
is most important.
Figure 1–2 RAID 1
Mirror 1
Data 1
Block 0-1
Block 2-3
Block 4-5
Block 0-1
Block 4-5
Block 2-3
SCSI-2
Disk Array Controller
SCSI
SCSI SCSI
In Figure 1–2 each segment is defined as 2 blocks of 512 bytes each.