From: Chris Murphy <lists@colorremedies.com>
To: Andrei Borzenkov <arvidjaar@gmail.com>
Cc: Hugo Mills <hugo@carfax.org.uk>,
Zygo Blaxell <ce3g8jdj@umail.furryterror.org>,
Chris Murphy <lists@colorremedies.com>,
kreijack@inwind.it, Roman Mamedov <rm@romanrm.net>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: Adventures in btrfs raid5 disk recovery
Date: Fri, 24 Jun 2016 11:06:09 -0600 [thread overview]
Message-ID: <CAJCQCtQBQAng5_mNJZev+64Z15BSkBkG9f2qmz=ckPRqXRbbWA@mail.gmail.com> (raw)
In-Reply-To: <CAA91j0Uqg0FafFTG3NhQt=p8KkYRhTeMU5Bd+JuUxDntP6g8Ng@mail.gmail.com>
On Fri, Jun 24, 2016 at 3:52 AM, Andrei Borzenkov <arvidjaar@gmail.com> wrote:
> On Fri, Jun 24, 2016 at 11:50 AM, Hugo Mills <hugo@carfax.org.uk> wrote:
>eta)data and RAID56 parity is not data.
>>
>> Checksums are not parity, correct. However, every data block
>> (including, I think, the parity) is checksummed and put into the csum
>> tree. This allows the FS to determine where damage has occurred,
>> rather thansimply detecting that it has occurred (which would be the
>> case if the parity doesn't match the data, or if the two copies of a
>> RAID-1 array don't match).
>>
>
> Yes, that is what I wrote below. But that means that RAID5 with one
> degraded disk won't be able to reconstruct data on this degraded disk
> because reconstructed extent content won't match checksum. Which kinda
> makes RAID5 pointless.
I don't understand this. Whether the failed disk means a stripe is
missing a data strip or parity strip, if any other strip is damaged of
course the reconstruction isn't going to match checksum. This does not
make raid5 pointless.
--
Chris Murphy
next prev parent reply other threads:[~2016-06-24 17:06 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-20 3:44 Adventures in btrfs raid5 disk recovery Zygo Blaxell
2016-06-20 18:13 ` Roman Mamedov
2016-06-20 19:11 ` Zygo Blaxell
2016-06-20 19:30 ` Chris Murphy
2016-06-20 20:40 ` Zygo Blaxell
2016-06-20 21:27 ` Chris Murphy
2016-06-21 1:55 ` Zygo Blaxell
2016-06-21 3:53 ` Zygo Blaxell
2016-06-22 17:14 ` Chris Murphy
2016-06-22 20:35 ` Zygo Blaxell
2016-06-23 19:32 ` Goffredo Baroncelli
2016-06-24 0:26 ` Chris Murphy
2016-06-24 1:47 ` Zygo Blaxell
2016-06-24 4:02 ` Andrei Borzenkov
2016-06-24 8:50 ` Hugo Mills
2016-06-24 9:52 ` Andrei Borzenkov
2016-06-24 10:16 ` Hugo Mills
2016-06-24 10:19 ` Andrei Borzenkov
2016-06-24 10:59 ` Hugo Mills
2016-06-24 11:36 ` Austin S. Hemmelgarn
2016-06-24 17:40 ` Chris Murphy
2016-06-24 18:06 ` Zygo Blaxell
2016-06-24 17:06 ` Chris Murphy [this message]
2016-06-24 17:21 ` Andrei Borzenkov
2016-06-24 17:52 ` Chris Murphy
2016-06-24 18:19 ` Austin S. Hemmelgarn
2016-06-25 16:44 ` Chris Murphy
2016-06-25 21:52 ` Chris Murphy
2016-06-26 7:54 ` Andrei Borzenkov
2016-06-26 15:03 ` Duncan
2016-06-26 19:30 ` Chris Murphy
2016-06-26 19:52 ` Zygo Blaxell
2016-06-27 11:21 ` Austin S. Hemmelgarn
2016-06-27 16:17 ` Chris Murphy
2016-06-27 20:54 ` Chris Murphy
2016-06-27 21:02 ` Henk Slager
2016-06-27 21:57 ` Zygo Blaxell
2016-06-27 22:30 ` Chris Murphy
2016-06-28 1:52 ` Zygo Blaxell
2016-06-28 2:39 ` Chris Murphy
2016-06-28 3:17 ` Zygo Blaxell
2016-06-28 11:23 ` Austin S. Hemmelgarn
2016-06-28 12:05 ` Austin S. Hemmelgarn
2016-06-28 12:14 ` Steven Haigh
2016-06-28 12:25 ` Austin S. Hemmelgarn
2016-06-28 16:40 ` Steven Haigh
2016-06-28 18:01 ` Chris Murphy
2016-06-28 18:17 ` Steven Haigh
2016-07-05 23:05 ` Chris Murphy
2016-07-06 11:51 ` Austin S. Hemmelgarn
2016-07-06 16:43 ` Chris Murphy
2016-07-06 17:18 ` Austin S. Hemmelgarn
2016-07-06 18:45 ` Chris Murphy
2016-07-06 19:15 ` Austin S. Hemmelgarn
2016-07-06 21:01 ` Chris Murphy
2016-06-24 16:52 ` Chris Murphy
2016-06-24 16:56 ` Hugo Mills
2016-06-24 16:39 ` Zygo Blaxell
2016-06-24 1:36 ` Zygo Blaxell
2016-06-23 23:37 ` Chris Murphy
2016-06-24 2:07 ` Zygo Blaxell
2016-06-24 5:20 ` Chris Murphy
2016-06-24 10:16 ` Andrei Borzenkov
2016-06-24 17:33 ` Chris Murphy
2016-06-24 11:24 ` Austin S. Hemmelgarn
2016-06-24 16:32 ` Zygo Blaxell
2016-06-24 2:17 ` Zygo Blaxell
2016-06-22 4:06 ` Adventures in btrfs raid5 disk recovery - update Zygo Blaxell
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