Disable zfs prefetch by default

[Ilya A. Arkhipov]

20.02.2015, 15:52, "Fabian Keil" <freebsd-listen at fabiankeil.de>:
> "Ilya A. Arkhipov" <rum1cro at yandex.ru> wrote:
>>  We have zfs prefetch enabled by default with > 4GB, but I didn't seen
>>  any case for using it, and all tuning guide saying to disable it.
>
> Which tuning guides are you referring to?
This one https://wiki.freebsd.org/ZFSTuningGuide

>>  Maybe we disable zfs prefetch by default ? Or could you please provide
>>  why it needed.
>
> Whether or not prefetching is useful depends on the workload
> and the setup.
>
> If you doubt that the prefetch default is useful for your workload
> (for example because your systems mainly do small "random" reads
> from "random" files), you can easily test this by disabling prefetching
> for a while.
>
> If this is too much work (or if no difference can be measured),
> the default is probably fine.
>
> Fabian

Actualy on all my servers(more 300 ^_^), I've disable prefetch because on all have the same issue:
http://i.imgur.com/aJNCiBK.png
http://i.imgur.com/Di3FuWw.png
http://i.imgur.com/uunH1k8.png
http://i.imgur.com/vjYiB2K.png


-- 
With Best Regards,
Ilya A. Arkhipov