Date: Sun, 24 Jan 2010 20:40:36 +0200 From: Dan Naumov <dan.naumov@gmail.com> To: Jason Edwards <sub.mesa@gmail.com>, FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, freebsd-questions@freebsd.org, freebsd-fs@freebsd.org Subject: Re: 8.0-RELEASE/amd64 - full ZFS install - low read and write disk performance Message-ID: <cf9b1ee01001241040mbfc5259rcc750333e5400403@mail.gmail.com> In-Reply-To: <883b2dc51001241034u40c97fdet83eb1e6edb5f4df4@mail.gmail.com> References: <883b2dc51001240905r4cfbf830i3b9b400969ac261b@mail.gmail.com> <cf9b1ee01001240942x46616003oa9b616ff8c046cb5@mail.gmail.com> <alpine.GSO.2.01.1001241159160.17824@freddy.simplesystems.org> <cf9b1ee01001241029g51ab9b56peb3f7df0eda299f1@mail.gmail.com> <883b2dc51001241034u40c97fdet83eb1e6edb5f4df4@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, Jan 24, 2010 at 8:34 PM, Jason Edwards <sub.mesa@gmail.com> wrote: >> ZFS writes to a mirror pair >> requires two independent writes. =A0If these writes go down independent = I/O >> paths, then there is hardly any overhead from the 2nd write. =A0If the >> writes >> go through a bandwidth-limited shared path then they will contend for th= at >> bandwidth and you will see much less write performance. > > What he said may confirm my suspicion on PCI. So if you could try the sam= e > with "real" Serial ATA via chipset or PCI-e controller you can confirm th= is > story. I would be very interested. :P > > Kind regards, > Jason This wouldn't explain why ZFS mirror on 2 disks directly, on the exact same controller (with the OS running off a separate disks) results in "expected" performance, while having the OS run off/on a ZFS mirror running on top of MBR-partitioned disks, on the same controller, results in very low speed. - Dan
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?cf9b1ee01001241040mbfc5259rcc750333e5400403>