zfs, nfs and zil
Alexander at Leidinger.net
Wed Mar 30 06:23:43 UTC 2011
Quoting Adam Vande More <amvandemore at gmail.com> (from Tue, 29 Mar 2011
> On Mon, Mar 28, 2011 at 11:46 AM, Claus Guttesen <kometen at gmail.com> wrote:
>> I'm aware of that, but the only way the problem shows up is when a
>> windows machine performs an installation or a windows update (and has
>> alot of updates in the pipeline). When traffic (i/o) is low to
>> moderate it justs goes along without any issues. And if the same
>> virtual windows-installation is on an iscsi-partition (mounted by the
>> vmware-server) I can't reproduce the problem. So if disabling the zil
>> did make a difference I would install a dedicated zil-ssd-device. And
>> if that did alleviate my problem the issue could be related to windows
>> performing alot of small reads and writes. Hence why I wanted to
>> disable the zil.
> What did someone say about shooting yourself on the foot?
Because without the ZIL there is no synchronous write (and IIRC no
fsync). Without such a sync-write/fsync your software gets an OK (data
on disk) when it isn't. The software may ACK to someone else the data
is safe and the other side marks the data as processed. When the
system crashes, this data is lost while the world thinks the data is
there. Every MTA is working like this. Databases rely on this too.
> I don't think you can even disable it on newer versions of ZFS so it may be
> something of a moot point.
Newer versions don't matter on 8.x for the moment.
I think we are in Rats Alley where the dead men lost their bones.
-- T. S. Eliot
http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7
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