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Date:      Thu, 28 Feb 2013 15:19:38 +0100
From:      Ivan Voras <ivoras@freebsd.org>
To:        freebsd-current@freebsd.org
Cc:        freebsd-fs@freebsd.org
Subject:   Re: Unexpected SU+J inconsistency AGAIN -- please, don't shift topic to ZFS!
Message-ID:  <kgnp1n$9mc$1@ger.gmane.org>
In-Reply-To: <583012022.20130228143129@serebryakov.spb.ru>
References:  <1796551389.20130228120630@serebryakov.spb.ru> <1238720635.20130228123325@serebryakov.spb.ru> <1158712592.20130228141323@serebryakov.spb.ru> <CAPJF9w=CZg_%2BK7NHTGUhRLaMJWWNOG7zMipGMJL6w6NoNZpSXA@mail.gmail.com> <583012022.20130228143129@serebryakov.spb.ru>

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On 28/02/2013 11:31, Lev Serebryakov wrote:

>  WD disks are in software RAID5 with geom_raid5 (from ports, but I'm
>  active maintainer of it).
>    Disks are in "Default" configuration: WC and NCQ are enabled.
>
>    I know, that FS guys could blame geom_raid5, as it could delay real
>  write up to 15 seconds, but it never "lies" about writes (it doesn't
>  mark BIOs complete till they are really sent to disk) and I could
>  not reproduce any problems with it on many hours tests on VMs (and I
>  don't want to experiment a lot on real hardware, as it contains my
>  real data).
>=20
>    Maybe, it is subtile interference between raid5 implementation and
>   SU+J, but in such case I want to understand what does raid5 do
>   wrong.

You guessed correctly, I was going to blame geom_raid5 :)

Is this a production setup you have? Can you afford to destroy it and
re-create it for the purpose of testing, this time with geom_raid3
(which should be synchronous with respect to writes)?


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