Date: Thu, 30 Dec 2010 19:58:37 -0700 From: David Samms <dsamms@nw-ds.com> To: freebsd-fs@freebsd.org Subject: Re: 8.2-RC1 and ZFS Message-ID: <ifjgsu$s33$1@dough.gmane.org> In-Reply-To: <ifidg5$qeq$1@dough.gmane.org> References: <4D1BCE34.4090601@nw-ds.com> <20101230085723.GA38391@tolstoy.tols.org> <ifidg5$qeq$1@dough.gmane.org>
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On 12/30/10 09:54, David Samms wrote: > 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. The same test with ZFSv28 and ZFSv28 + tuning ZFSv28 ---------------------------------------------------------------------- dd if=/dev/zero of=big bs=1m count=6400 6710886400 bytes transferred in 158.205268 secs (42418855 bytes/sec) OpenOffice 197sec MP3 skips XFCE4 popup menus took 5-15 seconds to appear ZFSv28 + tuning --vfs.zfs.txg.timeout="5" --vfs.zfs.txg.write_limit_override=268435456 --kern.maxvnodes=250000 ---------------------------------------------------------------------- dd if=/dev/zero of=big bs=1m count=6400 6710886400 bytes transferred in 167.316444 secs (40108947 bytes/sec) OpenOffice 190sec No MP3 skips during "dd", but one skip while OpenOffice was starting XFCE4 popup menus took 2-13 seconds to appear
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