Just in case the RAID5 maintainers aren't aware of it:What kind of "transient io error" would that be?
The current Linux kernel RAID5 implementation is just
too fragile to be used for most of the applications
where it would be most useful.
In principle, RAID5 should allow construction of a
disk-based store which is considerably MORE reliable
than any individual drive.
In my experience, at least, using Linux RAID5 results
in a disk storage system which is considerably LESS
reliable than the underlying drives.
What happens repeatedly, at least in my experience over
a variety of boxes running a variety of 2.4 and 2.6
Linux kernel releases, is that any transient I/O problem
results in a critical mass of RAID5 drives being marked
'failed',
at which point there is no longer any supportedAs other have showed - "mdadm" can reassemble your
way of retrieving the data on the RAID5 device, even
though the underlying drives are all fine, and the underlying
data on those drives almost certainly intact.