Date: Tue, 17 May 2016 16:35:49 -0500 From: "Matthew D. Fuller" <fullermd@over-yonder.net> To: Freddie Cash <fjwcash@gmail.com> Cc: Steven Hartland <steven@multiplay.co.uk>, "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? Message-ID: <20160517213549.GK24656@over-yonder.net> In-Reply-To: <CAOjFWZ6o8Gqh1BzUbkLj%2BKKXm=r2S-3qy_yk5k84Q57yj7FuAw@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> <CAOjFWZ6o8Gqh1BzUbkLj%2BKKXm=r2S-3qy_yk5k84Q57yj7FuAw@mail.gmail.com>
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On Tue, May 17, 2016 at 02:16:16PM -0700 I heard the voice of Freddie Cash, and lo! it spake thus: > > 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. More specifically, as I read it, different performance in a very specific metric; single-thread linear bulk writes. That doesn't seem like it would benefit heavily from a lot of cores available, or from RAM bandwidth or size above a pretty low threshold. Of course, it's not just changing the CPU and RAM; it's also the motherboard, and possibly the HBA (at least the bus the HBA is on, if it's a card being transplanted with the pool). And the Core 2 would be back in the plain-old FSB era, so RAM access would be competing with the disk IO on the bus. -- Matthew Fuller (MF4839) | fullermd@over-yonder.net Systems/Network Administrator | http://www.over-yonder.net/~fullermd/ On the Internet, nobody can hear you scream.
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