Date: Wed, 23 Jan 2013 13:10:54 -0800 From: Artem Belevich <art@freebsd.org> To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> Cc: freebsd-fs <freebsd-fs@freebsd.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: ZFS regimen: scrub, scrub, scrub and scrub again. Message-ID: <CAFqOu6hYiPDEpr9uQdE%2BCfmcL7%2Bhumpx2W7jcnLKcJdOG8bzFg@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1301232121430.1659@wojtek.tensor.gdynia.pl> References: <CACpH0Mf6sNb8JOsTzC%2BWSfQRB62%2BZn7VtzEnihEKmEV2aO2p%2Bw@mail.gmail.com> <alpine.BSF.2.00.1301211201570.9447@wojtek.tensor.gdynia.pl> <20130122073641.GH30633@server.rulingia.com> <alpine.BSF.2.00.1301232121430.1659@wojtek.tensor.gdynia.pl>
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On Wed, Jan 23, 2013 at 12:22 PM, Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> wrote: >>> While RAID-Z is already a king of bad performance, >> >> >> I don't believe RAID-Z is any worse than RAID5. Do you have any actual >> measurements to back up your claim? > > > it is clearly described even in ZFS papers. Both on reads and writes it > gives single drive random I/O performance. For reads - true. For writes it's probably behaves better than RAID5 as it does not have to go through read-modify-write for partial block updates. Search for RAID-5 write hole. If you need higher performance, build your pool out of multiple RAID-Z vdevs.
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