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Date:      Thu, 10 Jan 2013 11:18:58 +0100
From:      Johan Hendriks <joh.hendriks@gmail.com>
To:        Artem Belevich <art@freebsd.org>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: rc.d script for memory based zfs intent log
Message-ID:  <50EE9592.8050903@gmail.com>
In-Reply-To: <CAFqOu6hQvpJ6Z=rWFwu1hp9Yq6pii_hrhNta=L0b81ChKfEtKA@mail.gmail.com>
References:  <20130109023327.GA1888@FreeBSD.org> <AAEA3C3D-7FD5-4F26-A73B-47264F05E088@sarenet.es> <CAFqOu6hQvpJ6Z=rWFwu1hp9Yq6pii_hrhNta=L0b81ChKfEtKA@mail.gmail.com>

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Artem Belevich schreef:
> On Wed, Jan 9, 2013 at 7:15 AM, Borja Marcos <borjam@sarenet.es> wrote:
>> In case of a crash, seems to be riskier than using sync=disabled on the datasets you need.  What is the impact on the data integrity of a suddenly disappearing ZIL?
> Losing ZIL used to be fatal for the pool.
> I think in recent ZFS versions (v28?) you will only lose transactions
> that were not committed to the pool yet, but don't quote me on that.
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Loosing the ZIL will loose data written to the ZIL not jet flushed to 
the pool itself.
So most likely you will have corrupted data.
So for a ZIL use a mirror pair!
You can add and remove a ZIL from the pool without problem from version 
28 and above.

Same thing goes if you have sync=disabled.
Data acknowledge by the server but not flushed to the pool will end up 
in corrupt data.
Disabeling sync is something you do not want to do.
If you need, use the ZIL.

regards
Johan Hendriks
Neuteboom Automatisering






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