From: Bob Marley <bobmarley@shiftmail.org>
To: linux-btrfs@vger.kernel.org
Subject: Re: 1 week to rebuid 4x 3TB raid10 is a long time!
Date: Sun, 20 Jul 2014 23:28:24 +0200 [thread overview]
Message-ID: <53CC3478.8060503@shiftmail.org> (raw)
In-Reply-To: <20140721013609.6d99c399@natsu>
On 20/07/2014 21:36, Roman Mamedov wrote:
> On Sun, 20 Jul 2014 21:15:31 +0200
> Bob Marley <bobmarley@shiftmail.org> wrote:
>
>> Hi TM, are you doing other significant filesystem activity during this
>> rebuild, especially random accesses?
>> This can reduce performances a lot on HDDs.
>> E.g. if you were doing strenous multithreaded random writes in the
>> meanwhile, I could expect even less than 5MB/sec overall...
> I believe the problem here might be that a Btrfs rebuild *is* a strenuous
> random read (+ random-ish write) just by itself.
>
> Mdadm-based RAID would rebuild the array reading/writing disks in a completely
> linear manner, and it would finish an order of magnitude faster.
Now this explains a lot!
So they would just need to be sorted?
Sorting the files of a disk from lowest to highers block number prior to
starting reconstruction seems feasible. Maybe not all of them together
because they will be millions, but sorting them in chunks of 1000 files
would still produce a very significant speedup!
next prev parent reply other threads:[~2014-07-20 21:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-20 8:45 1 week to rebuid 4x 3TB raid10 is a long time! TM
2014-07-20 13:53 ` Duncan
2014-07-20 14:00 ` Tomasz Torcz
2014-07-20 14:50 ` Austin S Hemmelgarn
2014-07-20 17:15 ` ashford
2014-07-20 18:21 ` TM
2014-07-20 18:23 ` TM
2014-07-20 19:15 ` Bob Marley
2014-07-20 19:36 ` Roman Mamedov
2014-07-20 19:59 ` ashford
2014-07-21 2:48 ` Duncan
2014-07-21 16:46 ` ronnie sahlberg
2014-07-21 18:31 ` Chris Murphy
2014-07-22 2:51 ` Duncan
2014-07-22 17:13 ` Chris Murphy
2014-07-24 17:19 ` Chris Murphy
2014-07-20 21:28 ` Bob Marley [this message]
2014-07-20 21:54 ` George Mitchell
2014-07-21 1:22 ` Wang Shilong
2014-07-21 14:00 ` TM
2014-07-22 1:10 ` Wang Shilong
2014-07-22 1:17 ` Wang Shilong
2014-07-22 14:43 ` TM
2014-07-22 15:30 ` Stefan Behrens
2014-07-22 20:21 ` TM
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