[NCLUG] sw raid, recovery after install

[Bob Proulx]

Michael Milligan wrote:
> Yup.  Caveat being though that by the time you have a RAID mismatch,
> you've exhausted the drive (or drives!) bad-block remapping capability
> and are now teetering on the precipice of disaster.

I disagree because I think you are confusing array mismatches with
drive errors.  Those aren't related.  Once a drive starts to give you
block errors then of course what you say about exhausting the drives
spare blocks is true.  But if there aren't any drive errors then the
drive isn't having problems and the issue is the layer above them.

Array mismatches occur during normal operation of the array even with
perfect drives.  It is annoying that the check produces chatter but it
isn't really a problem.  It is just reporting raw information.  Raw
information that should be ignored.

> S.M.A.R.T.  monitoring is a better tool to watch for drives going
> bad.

Better?  Yes.  Good at it?  I don't think so.  And I am zeroing in on
the word "going" meaning prediction of drive problems in the future
tense.

I haven't seen SMART be a great predictor of drive failure.  I still
use SMART and think everyone else should too.  It is a good diagnostic
tool and is a good way to confirm a disk problem.  I always set up
routine SMART self-tests on drives with monitoring so that problems
are noticed.  It is a good monitor of the current drive state.

Bob