Date: Mon, 15 Jun 2009 08:47:45 -0700 From: George Hartzell <hartzell@alerce.com> To: Freddie Cash <fjwcash@gmail.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: Does this disk/filesystem layout look sane to you? Message-ID: <18998.27937.780804.279674@already.local> In-Reply-To: <b269bc570906141916k7bcf47b2pe87a88dde2d0a7a4@mail.gmail.com> References: <cf9b1ee00906140916n64a6c0cbr69332811bfa2aa62@mail.gmail.com> <cf9b1ee00906140917j86b1e4ev4f8e0a1fb5f6b8@mail.gmail.com> <b269bc570906141916k7bcf47b2pe87a88dde2d0a7a4@mail.gmail.com>
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Freddie Cash writes: > On Sun, Jun 14, 2009 at 9:17 AM, Dan Naumov <dan.naumov@gmail.com> wrote: > > > I just wanted to have an extra pair (or a dozen) of eyes look this > > configuration over before I commit to it (tested it in VMWare just in > > case, it works, so I am considering doing this on real hardware soon). > > I drew a nice diagram: http://www.pastebin.ca/1460089 Since it doesnt > > show on the diagram, let me clarify that the geom mirror consumers as > > well as the vdevz for ZFS RAIDZ are going to be partitions (raw disk > > => full disk slice => swap partition | mirror provider partition | zfs > > vdev partition | unused. > > > I don't know for sure if it's the same on FreeBSD, but on Solaris, ZFS will > disable the onboard disk cache if the vdevs are not whole disks. IOW, if > you use slices, partitions, or files, the onboard disk cache is disabled. > This can lead to poor write performance. > > Unless you can use one of the ZFS-on-root facilities, I'd look into getting > a couple of CompactFlash or USB sticks to use for the gmirror for / and /usr > (put the rest on ZFS). Then you can dedicate the entirety of all 5 drives > to ZFS. Even if you use do a bootable ZFS on root, you'll end up with a couple of gpt partitions (boot code, swap, then root) and therefor constructing your ZFS file system from a partition. Pawel said, back on April 6, 2007, "We support cache flushing operations on any GEOM provider (disk, partition, slice, anything disk-like), so bascially currently I treat everything as a whole disk [...]" Does anyone know for sure if we disable caching for partitions? g.
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