Date: Fri, 2 Dec 2011 19:36:44 GMT From: Martin Simmons <martin@lispworks.com> To: freebsd-fs@freebsd.org Subject: Re: Monitoring ZFS IO Message-ID: <201112021936.pB2Jaiuw012444@higson.cam.lispworks.com> In-Reply-To: <20111202153624.GA28715@icarus.home.lan> (message from Jeremy Chadwick on Fri, 2 Dec 2011 07:36:24 -0800) References: <4ED8D7A5.7090700@icritical.com> <op.v5u91pls8527sy@212-182-167-131.ip.telfort.nl> <4ED8EC9A.2080706@icritical.com> <20111202153624.GA28715@icarus.home.lan>
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>>>>> On Fri, 2 Dec 2011 07:36:24 -0800, Jeremy Chadwick said: > > On Fri, Dec 02, 2011 at 03:19:54PM +0000, Matt Burke wrote: > > On 12/02/11 14:47, Ronald Klop wrote: > > > while true; do gstat -b -I 1s; done > > > > Looks like I wasn't clear about what I'm after - sorry. > > > > I want to see how many bytes or KB have been read and written to a given > > zpool since creation (as in the newer of uptime or zpool creation) on the > > system. > > > > For instance I want this data: > > > > # time iostat -Idx > > extended device statistics > > device r/i w/i kr/i kw/i wait svc_t %b > > mfid0 284807.0 5469251.0 4452202.0 116634996.0 0 0.8 0 > > mfid1 284576.0 5466322.0 4474976.5 116510280.0 0 0.8 0 > > mfid2 278686.0 5450269.0 4418703.0 116511709.0 0 0.8 0 > > mfid3 281673.0 5452757.0 4439770.5 116560910.5 0 0.8 0 > > mfid4 279549.0 5472177.0 4440227.0 116609067.0 0 0.8 0 > > mfid5 282625.0 5464261.0 4503257.5 116608801.5 0 0.8 0 > > mfid6 275635.0 5470654.0 4433529.0 116616131.5 0 0.8 0 > > ... > > mfid27 302950.0 5464880.0 4434398.0 116542100.0 0 0.7 0 > > mfid28 281464.0 5459410.0 4461678.5 116595780.5 0 0.8 0 > > mfid29 277535.0 5468784.0 4443352.5 116642932.0 0 0.8 0 > > ... > > real 0m0.003s > > user 0m0.000s > > sys 0m0.007s > > > > > > For the zpool as a singular entitiy (or even by zfs filesystem), but not > > for the individual disks. > > > > Hope this clarifies my request a bit > > To my knowledge this kind of data is not kept/available in ZFS (FreeBSD > or Solaris). What you're wanting (truly) are counters rather than > averages, and you can do the averaging yourself (if wanted). "zpool > iostat" does not do this. > > With most utilities like iostat, mpstat, zpool iostat, gstat, vmstat, > and others of this nature, the established method/model/norm is that you > always provide an interval and you ignore the first sample/set of data > shown. In iostat's case on FreeBSD, it provides you an average over the > entire system uptime. Other utilities do not work this way. > > Even if "zpool iostat" behaved like your above iostat example, you'd > still run into the problem I described in my other mail (which is that > you get human-readable output, not actual integers/floats, and you > therefore have to do math to turn the values into integers, which sounds > easy but isn't, and you lose granularity/accuracy too). > > I cannot explain why "zpool iostat" (note no interval argument!) shows > some reads/writes. For example, on my systems, the following loop: > > while true; do zpool iostat; done > > ...literally returns the same data over and over, no matter what is > going on with he pools (reads or writes). I'm sure someone can explain > this behaviour, but it reminds me of systems where running "vmstat 1" > shows "crazy" values for the first interval, but the 2nd and onward > are accurate. It looks like the first set of numbers are the averages between now and the time that the vdev was loaded into the kernel (see print_vdev_stats). It should be easy to write a function that prints the unscaled raw values. __Martin
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