On Nov 8, 2011, at 6:38 AM, Evaldas Auryla wrote:

> Hi all,
> I'm trying to evaluate what are the risks of running NFS share of zfs dataset 
> with sync=disabled property. The clients are vmware hosts in our environment 
> and server is SunFire X4540 "Thor" system. Though general recommendation 
> tells not to do this, but after testing performance with default setting and 
> sync=disabled - it's night and day, so it's really tempting to do 
> sync=disabled ! Thanks for any suggestion.

The risks are, any changes your software clients expect to be written to disk 
-- after having gotten a confirmation that they did get written -- might not 
actually be written if the server crashes or loses power for some reason.

You should consider a high performance low-latency SSD (doesn't have to be very 
big) as an SLOG… it will do a lot for your performance without having to give 
up the commit guarantees that you lose with sync=disabled.

Of course, if the data isn't precious to you, then running with sync=disabled 
is probably ok.  But if you love your data, don't do it.

        - Garrett

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