I have 17 scsi disks, all 18 Gig.  I run a full scan each night.  I find
about 1 error each week.  The rate was much lower until a few months ago.
Mostly the same few disks.  Anyway, the errors are corrected by the scan
before md finds them.  Otherwise the errors could sit dormant for months
waiting for md to find 1, then while re-building to the spare md would find
another and poof!  Array gone.  Manual override needed to correct.  Since I
starting the scanning, md has not found any bad blocks.

The sad part, this is why I say Linux is not ready for prime time.  Ok for
home use, but not a 24x7 system that my job depends on!!!  If my job depends
on it, get an external hardware RAID system with battery backed memory.

Please, someone fix the bad block problems!!!
Without kicking out the disk as part of the solution!!!

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
owner@vger.kernel.org] On Behalf Of Mike Hardy
Sent: Tuesday, June 07, 2005 5:22 PM
To: Brad Campbell
Cc: Tom Eicher; linux-raid@vger.kernel.org
Subject: Re: entire array lost when some blocks unreadable?



Brad Campbell wrote:

quoted

Join the long line next to the club trophy cabinet :)

Its a shame the line is this long - I wish I had the time to implement
the solution myself, but not having that I can't really whine either.
Its still a shame though. Alas.

quoted

Something along those lines.
Generally if I get an error notification from smartd I pull the drive
from the array and re-add it. This causes a rewrite of the entire disk
and everyone is happy. (Unless the drive is dying, in which case the
rewrite of the entire disk usually finishes it off nicely)

When I get one of those, the first thing I do is verify my backup :-).
The backup is a second array that's on the network, so I typically
remount it read-only at that point.

Then I start drive scans on all drives (primary and backup) to see if
I've got any other blocks that will stop reconstruction. If I find any
other bad blocks on other devices, I immediately remount the primary as
read-only to preserve the data (if its not already gone) on all of the
disks. Note my disks almost never get written to, so this actually does
preserve the old data everywhere in all the cases I care about.

After that, a fail and re-add has done the trick for me in the past, but
once I actually got remapped into a bad block. Very annoying. Since
then, I fail the disk and do multiple badblocks passes on it.

Being able to enable an "aggressively correct" raid mode where any
single-block read error triggered a reconstruct/write/re-read cycle
until either it worked or failed would be nice. Bonus points for extra
md status markers that mdadm could pick up and mail to folks depending
on policy configuration.

-Mike
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