Date: Wed, 18 May 2016 08:49:34 -0500 (CDT) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Alex Tutubalin <lexa@lexa.ru> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? Message-ID: <alpine.GSO.2.20.1605180843280.7756@freddy.simplesystems.org> In-Reply-To: <f1cc3ee5-c141-b366-83bf-3ee0179381bf@lexa.ru> 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> <f1cc3ee5-c141-b366-83bf-3ee0179381bf@lexa.ru>
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On Wed, 18 May 2016, Alex Tutubalin wrote: > > If so, raidz will have huge write performance benefit in my case: single > write of one large file. This is not proven in practice. With mirrors one typically has more vdevs and each vdev gets a zfs block-size write in turn, using a round robin agorithm (tuned for available space vdev). Drive IOPs are saved since the blocks are not diced into smaller fragments (as raidzN requires). With raidz it is necessary to also pay the cost of the parity computations, which are not needed with mirroring. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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