Date: Tue, 17 May 2016 14:16:16 -0700 From: Freddie Cash <fjwcash@gmail.com> To: Steven Hartland <steven@multiplay.co.uk> Cc: "Brandon J. Wandersee" <brandon.wandersee@gmail.com>, "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? Message-ID: <CAOjFWZ6o8Gqh1BzUbkLj%2BKKXm=r2S-3qy_yk5k84Q57yj7FuAw@mail.gmail.com> In-Reply-To: <CAHEMsqZto0wD9Ko4E9YUpYvea4jM0E4f2nC1HkAwcCG=6DfX-A@mail.gmail.com> References: <8441f4c0-f8d1-f540-b928-7ae60998ba8e@lexa.ru> <f87ec54a-104e-e712-7793-86c37285fdaa@internetx.com> <16e474da-6b20-2e51-9981-3c262eaff350@lexa.ru> <BD7DE274-04EB-4B19-988D-5A6FADC5B51A@digsys.bg> <1e012e43-a49b-6923-3f0a-ee77a5c8fa70@lexa.ru> <86shxgsdzh.fsf@WorkBox.Home> <CAHEMsqZto0wD9Ko4E9YUpYvea4jM0E4f2nC1HkAwcCG=6DfX-A@mail.gmail.com>
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On Tue, May 17, 2016 at 2:11 PM, Steven Hartland <steven@multiplay.co.uk> wrote: > Raidz is limited essential limited to a single drive performance > per dev for read and write while mirror is single drive performance for > write its number of drives for read. Don't forget mirror is not limited t= o > two it can be three, four or more; so if you need more read throughput yo= u > can add drives to the mirror. > > To increase raidz performance you need to add more vdevs. While this > doesn't have to be double i.e. the same vdev config as the first it > generally a good idea. > > Don't forget that while it rebalances write performance of a multi vdev > raidz will be limited to the added vdev. > =E2=80=8BEverybody is missing the point of the OP. They're not asking for ways to improve the performance of a raidz-based pool; they're asking why they get different performance metrics from the exact same pool when they change the CPU and RAM. And, more importantly, why a Core-i3-based system shows better performance than a Core-i7-based system.=E2=80=8B Is there something inherent to the w= ay ZFS works that favours one setup over another (lower CPU core counts running at higher speeds is better/worse than higher CPU core counts running at lower speeds; more RAM channels is better/worse; things like that). --=20 Freddie Cash fjwcash@gmail.com
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