NFS home directory performance tuning for Linux client

CyberLeo Kitsana cyberleo at
Tue Aug 29 22:21:11 UTC 2017

On 08/21/2017 01:47 PM, Kaya Saman wrote:
> So, currently I've tried doing something a little different which worked
> out well.<snip>
> The bottleneck was definitely caused by NFS and I think it was the write
> behaviour for small files, with the limited options available though I
> have no idea what could be causing the issues or how to get round them??

Try setting sync=disabled on the zfs datasets backing your NFS shares.
If this has a noticeable impact on performance, you may instead want to
invest in a SLOG device. This can be a mirrored pair of
high-iops/low-latency SSDs, or a battery-backed RAM device.

Ordinarily, the ZIL is on the pool's main storage. If you have a bunch
of high-latency spinning disks, this can slow sync writes way down as
they then have to wait for the disks to finish. An external ZIL on a
fast SLOG device will boost sync writes closer to the throughput of the
SLOG than the pool.

If I remember correctly, all NFS writes are sync writes, and will be
impacted by the latency of the ZIL. Setting sync to disabled on a
dataset will eliminate the guarantees of sync writes (data loss possible
in the case of crash or power loss) but may speed up NFS through this
compromise. I would not recommend leaving sync disabled, though.

Fuzzy love,

<CyberLeo at CyberLeo.Net>
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