From: Wols Lists <antlists@youngman.org.uk>
To: Nix <nix@esperi.org.uk>, NeilBrown <neilb@suse.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: 4.11.2: reshape raid5 -> raid6 atop bcache deadlocks at start on md_attr_store / raid5_make_request
Date: Mon, 22 May 2017 20:07:18 +0100 [thread overview]
Message-ID: <592336E6.8080906@youngman.org.uk> (raw)
In-Reply-To: <87o9ukykmk.fsf@esperi.org.uk>
On 22/05/17 16:30, Nix wrote:
> I'll give it a try -- I hit it twice in succession, once with a
> --backup-file, once without. Since mdadm does not warn about the lack of
> a --backup-file, I guess the statement in the manual that it is
> essential to provide one when changing RAID levels is untrue: I suspect
> that it's necessary *if* you're not increasing the number of disks at
> the same time, but since I'm growing into a spare, adding a
> --backup-file only slows it down?
I did discuss this with Neil while I wrote it, so I hope I got it right :-)
https://raid.wiki.kernel.org/index.php/A_guide_to_mdadm#Array_internals_and_how_it_affects_mdadm
aiui, provided you're using a v1 superblock, the data offset means there
is spare space on the drives precisely for the purpose (one of then at
least) of keeping a backup. So the reshape will start reshaping into the
spare space and eliminate the need for the backup - the new version of
the stripe will be safely written before the space occupied by the old
stripe is required.
Cheers,
Wol
next prev parent reply other threads:[~2017-05-22 19:07 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-22 9:13 4.11.2: reshape raid5 -> raid6 atop bcache deadlocks at start on md_attr_store / raid5_make_request Nix
2017-05-22 11:35 ` NeilBrown
2017-05-22 15:30 ` Nix
2017-05-22 19:07 ` Wols Lists [this message]
2017-05-22 20:43 ` Nix
2017-05-23 1:20 ` NeilBrown
2017-05-23 10:10 ` Nix
2017-05-23 1:39 ` NeilBrown
2017-05-23 14:47 ` Wols Lists
2017-05-24 1:50 ` NeilBrown
2017-05-23 1:07 ` NeilBrown
2017-05-22 21:38 ` Nix
2017-05-23 14:16 ` Wols Lists
2017-05-23 15:00 ` Nix
2017-05-24 1:24 ` NeilBrown
2017-05-24 13:28 ` Nix
2017-05-25 1:31 ` NeilBrown
2017-05-25 12:14 ` Nix
2017-05-24 19:42 ` Nix
2017-05-24 22:57 ` Shaohua Li
2017-05-25 1:30 ` NeilBrown
2017-05-25 1:46 ` Shaohua Li
2017-05-26 3:23 ` NeilBrown
2017-05-26 16:40 ` Shaohua Li
2017-05-28 23:17 ` NeilBrown
2017-05-30 17:41 ` Shaohua Li
2017-06-05 6:49 ` [PATCH] md: fix deadlock between mddev_suspend() and md_write_start() NeilBrown
2017-06-06 0:01 ` Shaohua Li
2017-06-07 1:45 ` NeilBrown
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