other RAID TYPES

RAID 2
As all hard disks have ECC data built into every sector, this configuration has no advantages over RAID 3 and is not used.

RAID 3
A single disk holds the parity information and the data integrity checking relies on ECC on the disk drives themselves, as with RAID 2. Because parity information is held on a dedicated drive, any single drive in the array can fail without data being lost.

Data can be rebuilt onto a replacement drive using the remaining information and the parity information. To maintain performance when transferring small files, synchronized motors may be required on each disk. Read and write operations cannot be overlapped, but as consecutive reads can occur on each drive at the same time, read performance is improved.

RAID 4
This is a faster version of RAID 3, in that the complete read of a file can occur on a single disk. Write performance is not improved as the parity drive needs updating with every write operation. As there are no real benefits over RAID 3 and write performance is worse than RAID 5, this configuration is not used.