Date: Fri, 20 Feb 2015 13:53:00 +0100 From: Fabian Keil <freebsd-listen@fabiankeil.de> To: "Ilya A. Arkhipov" <rum1cro@yandex.ru> Cc: freebsd-fs@freebsd.org Subject: Re: Disable zfs prefetch by default Message-ID: <66c5011b.0fcc09f9@fabiankeil.de> In-Reply-To: <54E71E20.8080303@yandex.ru> References: <54E71E20.8080303@yandex.ru>
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--Sig_/uyr9CYr8H=VxInaCrbfuAtz Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable "Ilya A. Arkhipov" <rum1cro@yandex.ru> wrote: > We have zfs prefetch enabled by default with > 4GB, but I didn't seen=20 > any case for using it, and all tuning guide saying to disable it. Which tuning guides are you referring to? > Maybe we disable zfs prefetch by default ? Or could you please provide=20 > 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 --Sig_/uyr9CYr8H=VxInaCrbfuAtz Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlTnLiYACgkQBYqIVf93VJ1lQACgyWFW051g5fIETiUbLJI5EgCX wsUAn0bhu3VQHmU21DZchVoWcmIKDMle =K0pp -----END PGP SIGNATURE----- --Sig_/uyr9CYr8H=VxInaCrbfuAtz--
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