RAID 6
RAID 6 stripes data across all disks in the array.
In addition to data, RAID 6 also writes array P and Q parity data. The P and Q parity data, which is based on Reed Solomon algorithms, is spread across all the disks. For a RAID 6 array of four disks, array data and parity information are written in the following pattern:
If one or two disks fail in a RAID 6 array, you can continue to use the array normally. A RAID 6 array operating with one or two failed disks is said to be operating in degraded mode. Whenever data is read from a degraded disk array, the array controller recalculates the data on the failed disks by using data and parity blocks on the operational disks. A RAID 6 array with a single failed disk has similar protection to that of a RAID 5 array with no disk failures. If a third disk fails, the array will be placed in the failed state and will not be accessible.
