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Date: Fri, 20 Sep 2013 17:11:01 +0200
From: Volker Armin Hemmann <volkerarmin@googlemail.com>
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Subject: Re: [gentoo-user] ZFS
References: <CAN0CFw1nGVZxJGGsq4TZidEPuyLDkcD0oYRDOOfNzFFM2vQ-tg@mail.gmail.com> <523898A3.7000404@googlemail.com> <523978b4.H704k8Gaca/dZ9jF%Joerg.Schilling@fokus.fraunhofer.de> <5239DD31.9080209@googlemail.com> <CAN0CFw2L52jSyarbzqPAbD_vNUmg48xfV7hAZo79+U4HN3CZ+w@mail.gmail.com>
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Am 19.09.2013 06:47, schrieb Grant:
>>>> turn off readahead. ZFS' own readahead and the kernel's clash - badly.
>>>> Turn off kernel's readahead for a visible performance boon.
>>> You are probably not talking about ZFS readahead but about the ARC.
>> which does prefetching. So yes.
> I'm taking notes on this so I want to clarify, when using ZFS,
> readahead in the kernel should be disabled by using blockdev to set it
> to 8?
>
> - Grant
>
> .
>
you can't turn it off (afaik) but 8 is a good value - because it is just
a 4k block.