RAID Array Controller
RAID 1
RAID 1 (also known as mirroring or shadowing) takes data sent by the host and duplicates it on all the drives in an array. The result is a high degree of data availability, since you can lose all but one drive in the array and still have full access to your data. This high degree of data availability comes at a price: a RAID 1 array requires multiple drives to achieve the storage capacity of a single drive. Figure
Figure 2-5. Diagram of a RAID 1 write
A RAID 1 array will show up on the monitor as degraded when at least one drive fails, even if two or more members of the redundancy group remain in good working order. As long as at least two working drives remain in the array, you may continue to run the array in degraded mode without putting data in jeopardy.
RAID 0+1
RAID 0+1 combines RAID 0 (striping) with RAID 1 (mirroring). In RAID 0+1 write, the controller breaks up the data block from the host into smaller chunks, then writes the chunks to half the drives in the array, while writing duplicate chunks to the remaining drives.
