RAID 5 arrays require a minimum configuration of three drives with the data stored in stripes. In an array with 4 drives, each stripe contains 3 data blocks and a single parity block. For each stripe, the parity block 'rotates' to the next drive in the sequence. In the diagram above you can see that in stripe 'A' parity is on disk 3, on stripe 'B' the parity has 'rotated' to Disk 2. Hence the term 'Striping with rotating parity'
RAID 5 can be used for all types of data storage. Because of the parity block in each stripe, it offers the security of redundancy. If a single drive fails, the data is still accessible from the remaining drives in the array. Where hot spares are used, the system will automatically rebuild on detection of a drive failure. However, If a second drive fails, then the system will halt.
If you would like to talk to a RAID data recovery engineer about the problem with your system please phone free 0800 072 3282