Troubles getting a software RAID 5 to work correctly
kenneth at mail1.ttak.org
Fri Nov 24 18:06:18 MST 2006
Nicholas Leippe wrote:
> [UU_] indicates that the array is degraded. Either a device has failed (or is
> in failure mode because you told it so), or it has not completed
> reconstruction (it remains degraded until this is done).
> When you first create a raid5 array, it computes the parity across the entire
> volume. (I know, kinda dumb when the data is all junk.)
> from man mdadm(8):
> When creating a RAID5 array, mdadm will automatically create a degraded array
> with an extra spare drive. This is because building the spare into a
> degraded array is in general faster than resyncing the parity on a
> non-degraded, but not clean, array. This feature can be over-ridden with
> the --force option.
> Until it finishes adding the third drive into the array, removing either of
> the others fails the array completely--IOW all of the data is now lost.
> I don't recall if you need to manually tell it to use the spare (I usually
> use --force on a new array). If /proc/mdadm does not show that
> reconstruction is in progress, then you'll have to tell it to do it.
Thank you for your response.
If I have already created the array, and it does not appear to be
"processing" the spare into the array, how do I force it to begin
processing? I did not see an option in the man pages about forcing the
processing of a spare.
More information about the PLUG