Date: Tue, 17 May 2016 22:46:44 +0100 From: Steven Hartland <steven@multiplay.co.uk> To: "Matthew D. Fuller" <fullermd@over-yonder.net> Cc: Freddie Cash <fjwcash@gmail.com>, "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? Message-ID: <CAHEMsqYNHtzy=NT%2Ba9pMw3n61ys4jTCfuAxY%2BDfFjLYBOmcqjQ@mail.gmail.com> In-Reply-To: <20160517213549.GK24656@over-yonder.net> 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> <20160517213549.GK24656@over-yonder.net>
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Not to mention it's so easy to cripple performance with a bad bios setup this could easily be a simple setup issue. I had an issue the other day where a 4ghz Intel CPU couldn't process video transcode in real time which turned out to be a power saving option in the bios that was utterly destroying performance by running the CPU at 800Mhz instead of 4Ghz. Everything else seemed fine with nothing was using more then a few present of CPU. Disabling power saving fixed the issue. This issue was not present on a much lower power / older box simply because it didn't have the advanced power saving options. I'm not saying this was the case in these tests but simply providing a comcrete example that it's sometimes hard to get like for like comparisons even for what should be simple tests. On Tuesday, 17 May 2016, Matthew D. Fuller <fullermd@over-yonder.net> wrote: > 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 <javascript:;> > Systems/Network Administrator | http://www.over-yonder.net/~fullermd/ > On the Internet, nobody can hear you scream. >
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