----- Original Message -----
From: "MRK" <mrk@xxxxxxxxxxxxx>
To: "Neil Brown" <neilb@xxxxxxx>
Cc: "Janos Haar" <janos.haar@xxxxxxxxxxxx>; <linux-raid@xxxxxxxxxxxxxxx>
Sent: Monday, May 03, 2010 12:04 PM
Subject: Re: Suggestion needed for fixing RAID6
On 05/03/2010 04:17 AM, Neil Brown wrote:
On Sat, 1 May 2010 23:44:04 +0200
"Janos Haar"<janos.haar@xxxxxxxxxxxx> wrote:
The general problem is, i have one single-degraded RAID6 + 2 badblock
disk
inside wich have bads in different location.
The big question is how to keep the integrity or how to do the rebuild
by 2
step instead of one continous?
Once you have the fix that has already been discussed in this thread, the
only other problem I can see with this situation is if attempts to write
good
data over the read-errors results in a write-error which causes the
device to
be evicted from the array.
And I think you have reported getting write
errors.
His dmesg AFAIR has never reported any error of the kind "raid5:%s: read
error NOT corrected!! " (the error message you get on failed rewrite
AFAIU)
Up to now (after my patch) he only tried with MD above DM-COW and DM was
dropping the drive on read error so I think MD didn't get any opportunity
to rewrite.
It is not clear to me what kind of error MD got from DM:
Apr 29 09:50:29 Clarus-gl2k10-2 kernel: device-mapper: snapshots:
Invalidating snapshot: Error reading/writing.
Apr 29 09:50:29 Clarus-gl2k10-2 kernel: ata8: EH complete
Apr 29 09:50:29 Clarus-gl2k10-2 kernel: raid5: Disk failure on dm-1,
disabling device.
I don't understand from what place the md_error() is called...
but also in this case it doesn't look like a rewrite error...
I think without DM COW it should probably work in his case.
Your new patch skips the rewriting and keeps the unreadable sectors,
right? So that the drive isn't dropped on rewrite...
The following patch should address this issue for you.
It is*not* a general-purpose fix, but a specific fix
[CUT]
Just a little note:
I have 2 bad drives, one wich have bads at 54%, have >2500 UNC sectors, wich
is too much for trying it to repair, this drive is really failing....
The other have only 123 bads at 99% wich is a very small scratch on the
platter, now i am trying to fix this drive instead.
The repair-check sync process now runs, i will reply soon again...
Thanks,
Janos
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