Date: Thu, 30 Dec 2010 09:54:28 -0700 From: David Samms <dsamms@nw-ds.com> To: freebsd-fs@freebsd.org Subject: Re: 8.2-RC1 and ZFS Message-ID: <ifidg5$qeq$1@dough.gmane.org> In-Reply-To: <20101230085723.GA38391@tolstoy.tols.org> References: <4D1BCE34.4090601@nw-ds.com> <20101230085723.GA38391@tolstoy.tols.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 12/30/10 01:57, Marco van Tol wrote: > On Wed, Dec 29, 2010 at 05:11:32PM -0700, David Samms wrote: >> I gave ZFS a try again this afternoon and immediately came across what I >> would consider a problem. Simply running dd causes such IO contention >> that a GUI desktop is unusable and MP3s stop playing. The problem is >> very repeatable, just run dd if=/dev/zero of=big bs=1m count=6400 >> >> System is amd64, source updated Dec 27. Default ZFS parameters. (no >> tuning). With the same system but UFS+s dd causes no problems. > > Check out this mail from Jeremy Chadwick from December 28th in > freebsd-stable@. > http://docs.freebsd.org/cgi/getmsg.cgi?fetch=312384+0+current/freebsd-stable > > I think specifically the comments and tweaks regarding > vfs.zfs.txg.timeout="5" and vfs.zfs.txg.write_limit_override=1073741824 > should be usefull for you. :-) > > I'm intentionally not touching the subject why you see what you do > without tuning. I'm sure there are a great bunch of different > situations for which the defaults are the way they are. > > :-) > > Marco van Tol > Marco, thank you for your reply. Jeremy, thank you for your tuning suggestions. It does appear that the default setting for ZFS are NOT well suited for a single drive setup. Based on Jeremy's suggestions I made the following changes from the defaults: vfs.zfs.txg.timeout="5" vfs.zfs.txg.write_limit_override=268435456 # (System has 4G of RAM) kern.maxvnodes=250000 I tested both UFS+s and ZFS for desktop usability while running "dd" to create IO contention. System has two identical 300G WD drives that are about 4 years old. For testing I switch at boot between the drives, one is ZFS the other UFS+s. Test was performed using XFCE4 with xmms playing MP3s while "dd" was creating a large file and OpenOffice was launching. ZFS ---------------------------------------------------------------------- %dd if=/dev/zero of=big bs=1m count=6400 6710886400 bytes transferred in 177.418146 secs (37825254 bytes/sec) openoffice startup about 185 sec No MP3 skips XFCE4 popup menus took 1-3 seconds to appear UFS+s ---------------------------------------------------------------------- dd if=/dev/zero of=big bs=1m count=6400 6710886400 bytes transferred in 165.061623 secs (40656855 bytes/sec) openoffice startup about 185 sec No MP3 skips XFCE4 popup menus took 5-25 seconds to appear While dd IO was slower with the new ZFS parameters, the desktop was very usable, and its responsiveness was better than USF+s. I will be upgrading to ZFSv28 and repeating this rudimentary desktop usability test.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ifidg5$qeq$1>