zfs, nfs and zil

[Claus Guttesen]

>> I'm mounting the FreeBSD-server from a couple of vmware esxi 4.1
>> servers using nfs, but when there is alot of i/o the server becomes
>> unresponsive, easily triggered by installing ie. ms-sql. The server
>> itself is up but is not reachable from the network. When I take the
>> nic down and up again connection to the network is reestablished
>> (ip-wise).
>>
>> A friend of mine has suggested that I disable the zil. The page
>> http://wiki.freebsd.org/ZFSTuningGuide says 'Disabling ZIL is not
>> recommended where data consistency is required (such as database
>> servers) but will not result in file system corruption.'
>>
>> Has anyone tried to disable zil and achieved better performance and
>> still maintain a consistent filesystem?
>
> The ZIL is not linked to NIC down/up events. It is a completely different
> topic. I suggest to find the real problem instead of doing some random
> tuning (which is not tuning in this case but foot-shooting).

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.

> FYI: disabling the ZIL is someting to do if you are desperate, do not care
> about production incidents, and everything else (if the ZIL is the problem
> -- which most probably it isn't by reading your message -- a (maybe write
> optimized) SSD as a log device could be a solution) does not solve the
> issue.

Thank you for your input. I will get a ssd-drive.

-- 
regards
Claus

When lenity and cruelty play for a kingdom,
the gentler gamester is the soonest winner.

Shakespeare

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