From: John Robinson <john.robinson@yuiop.co.uk>
To: keld@keldix.com
Cc: NeilBrown <neilb@suse.de>, Jakub Hus?k <jakub@gooseman.cz>,
Mikael Abrahamsson <swmike@swm.pp.se>,
linux-raid@vger.kernel.org
Subject: Re: bug: 4-disk md raid10 far2 can be assembled clean with only two disks, causing silent data corruption
Date: Wed, 26 Sep 2012 09:59:42 +0100 [thread overview]
Message-ID: <5062C3FE.7090906@yuiop.co.uk> (raw)
In-Reply-To: <20120926082848.GA18616@www5.open-std.org>
On 26/09/2012 09:28, keld@keldix.com wrote:
[...]
> I also understand it now, I think. raid10,f2 with 4 disks cannot in the current implementation
> survive 2 failing disks.
It can, but only two non-adjacent discs. With 4 drives sda-sdd, than
means you can only lose both sda and sdc, or sdb and sdd.
> We have discussed earlier how to implement raid10,far that would mean
> better survival chances with more disks failing. This is not implemented yet.
No, but even if/when it is, there will still be some combinations of two
discs that you cannot afford to lose. The layout change to try to
improve redundancy will not be generic, as it doesn't work for an odd
number of discs, so the existing layout would have to be retained as an
option.
Cheers,
John.
--
John Robinson, yuiop IT services
0131 557 9577 / 07771 784 058
46/12 Broughton Road, Edinburgh EH7 4EE
next prev parent reply other threads:[~2012-09-26 8:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-24 13:37 bug: 4-disk md raid10 far2 can be assembled clean with only two disks, causing silent data corruption Jakub Husák
2012-09-25 4:19 ` NeilBrown
2012-09-25 5:00 ` Mikael Abrahamsson
2012-09-25 9:48 ` jakub
2012-09-25 11:14 ` keld
2012-09-25 11:47 ` John Robinson
2012-09-25 12:32 ` NeilBrown
[not found] ` <50628B39.90205@gooseman.cz>
2012-09-26 5:41 ` NeilBrown
2012-09-26 8:28 ` keld
2012-09-26 8:59 ` John Robinson [this message]
2012-09-26 9:08 ` keld
2012-09-26 9:23 ` keld
[not found] ` <5067F014.5020600@gooseman.cz>
2012-09-30 10:24 ` keld
[not found] <50601CED.1050607@gooseman.cz>
2012-09-24 8:46 ` bug: 4-disk md raid10 far2 can be assembled clean with only two disks, causing "silent" " Jakub Husák
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