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.
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.