fsck'ing a Vinum RAID5 volume (and a stale drive)

[Daniel Eriksson]

Benjamin P. Keating wrote:

> Is
> this approach correct? does this do anything productive or just forces
> the state label to change and do nothing to the drives? I don't feel
> confident that it did anything and Im having a VERY hard time finding
> documentation on this.

Let me give you an example of a valid setstate use case:

One of my servers has a LOT of discs. For some reason I suffer from
interrupt storms during device probing (started after I added a second
Highpoint RocketRAID 454 to the machine). These storms sometime prevent the
ata code from detecting all the discs. If this happens to be a disc that is
part of a RAID-0 array, then when vinum starts up it detects that one of the
discs have disappeared and (correctly) marks the array as crashed. There is
no "proper" way to recover from a crashed RAID-0 array - your data is
normally lost forever. However, in this specific case I _know_ that nothing
has been written to the discs, so once I get the missing disc back online I
can use setstate to change the array status from crashed to up, confident
that no data has actually been lost.

There are a few other use cases for setstate, but they are all (?) outside
of the normal procedures for using and maintaining RAID arrays.

/Daniel Eriksson