From: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
To: Goffredo Baroncelli <kreijack@inwind.it>
Cc: Qu Wenruo <quwenruo@cn.fujitsu.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] btrfs: raid56: Use correct stolen pages to calculate P/Q
Date: Sun, 27 Nov 2016 11:53:55 -0500 [thread overview]
Message-ID: <20161127165355.GL8685@hungrycats.org> (raw)
In-Reply-To: <59e0b1c7-51a9-ede4-6571-fa0b20394145@inwind.it>
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On Sun, Nov 27, 2016 at 12:16:34AM +0100, Goffredo Baroncelli wrote:
> On 2016-11-26 19:54, Zygo Blaxell wrote:
> > On Sat, Nov 26, 2016 at 02:12:56PM +0100, Goffredo Baroncelli wrote:
> >> On 2016-11-25 05:31, Zygo Blaxell wrote:
> [...]
> >>
> >> BTW Btrfs in RAID1 mode corrects the data even in the read case. So
> >
> > Have you tested this? I think you'll find that it doesn't.
>
> Yes I tested it; and it does the rebuild automatically.
> I corrupted a disk of mirror, then I read the related file. The log says:
>
> [ 59.287748] BTRFS warning (device vdb): csum failed ino 257 off 0 csum 12813760 expected csum 3114703128
> [ 59.291542] BTRFS warning (device vdb): csum failed ino 257 off 0 csum 12813760 expected csum 3114703128
> [ 59.294950] BTRFS info (device vdb): read error corrected: ino 257 off 0 (dev /dev/vdb sector 2154496)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> IIRC In case of RAID5/6 the last line is missing. However in both the
> case the data returned is good; but in RAID1 the data is corrected
> also on the disk.
>
> Where you read that the data is not rebuild automatically ?
Experience? I have real disk failures all the time. Errors on RAID1
arrays persist until scrubbed.
No, wait... _transid_ errors always persist until scrubbed. csum failures
are rewritten in repair_io_failure. There is a comment earlier in
repair_io_failure that rewrite in RAID56 is not supported yet.
> In fact I was surprised that RAID5/6 behaves differently....
The difference is surprising, no matter which strategy you believe
is correct. ;)
> >> I am still convinced that is the RAID5/6 behavior "strange".
> >>
> >> BR
> >> G.Baroncelli
> >> --
> >> gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
> >> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5
> >>
>
>
> --
> gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5
>
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next prev parent reply other threads:[~2016-11-27 16:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-21 8:50 [PATCH] btrfs: raid56: Use correct stolen pages to calculate P/Q Qu Wenruo
2016-11-21 18:48 ` Goffredo Baroncelli
2016-11-22 0:28 ` Qu Wenruo
2016-11-22 18:02 ` Goffredo Baroncelli
2016-11-25 4:31 ` Zygo Blaxell
2016-11-25 4:40 ` Gareth Pye
2016-11-25 5:07 ` Zygo Blaxell
2016-11-26 13:12 ` Goffredo Baroncelli
2016-11-26 18:54 ` Zygo Blaxell
2016-11-26 23:16 ` Goffredo Baroncelli
2016-11-27 16:53 ` Zygo Blaxell [this message]
2016-11-28 0:40 ` Qu Wenruo
2016-11-28 18:45 ` Goffredo Baroncelli
2016-11-28 19:01 ` Christoph Anton Mitterer
2016-11-28 19:39 ` Austin S. Hemmelgarn
2016-11-28 3:37 ` Christoph Anton Mitterer
2016-11-28 3:53 ` Andrei Borzenkov
2016-11-28 4:01 ` Christoph Anton Mitterer
2016-11-28 18:32 ` Goffredo Baroncelli
2016-11-28 19:00 ` Christoph Anton Mitterer
2016-11-28 21:48 ` Zygo Blaxell
2016-11-29 1:52 ` Christoph Anton Mitterer
2016-11-29 3:19 ` Zygo Blaxell
2016-11-29 7:35 ` Adam Borowski
2016-11-29 14:24 ` Christoph Anton Mitterer
2016-11-22 18:58 ` Chris Mason
2016-11-23 0:26 ` Qu Wenruo
2016-11-26 17:18 ` Chris Mason
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