Date: Sat, 20 Feb 2010 15:48:45 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Boris Samorodov <bsam@ipt.ru> Cc: freebsd-questions@freebsd.org Subject: Re: strange disk activity Message-ID: <20100220214845.GI70798@dan.emsphone.com> In-Reply-To: <88797383@ipt.ru> References: <97752307@ipt.ru> <20100220202614.GG70798@dan.emsphone.com> <88797383@ipt.ru>
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In the last episode (Feb 20), Boris Samorodov said:
> On Sat, 20 Feb 2010 14:26:15 -0600 Dan Nelson wrote:
> > In the last episode (Feb 20), Boris Samorodov said:
> > > Hello List,
> > >
> > > I've got a very strange disk activity:
> > > -----
> > > % iostat -xw60 da0
> > > extended device statistics
> > > device r/s w/s kr/s kw/s wait svc_t b
> > > da0 43.2 204.4 971.9 10917.2 0 30.7 30
> > > extended device statistics
> > > device r/s w/s kr/s kw/s wait svc_t b
> > > da0 5.1 274.6 72.7 15206.2 0 50.4 27
> > >
> > > If I'm not mistaken it's approx. 15Mb/sec. Which means more than 1000 Tb a
> > > day!
> > >
> > > How can I find which program is trashing the disk? The system is
> > > FreeBSD-7.0 with 15 jails. Thanks for your help.
>
> > Something like this would be a good start:
>
> > dtrace -n 'syscall::write:entry { @dist[pid,execname] = sum(arg2); }'
>
> > Let it run a few seconds, then hit ^C, and it will print the total bytes
> > written by each process during that period. You may also have to trace
> > writev and pwrite, since FreeBSD's dtrace doesn't include the sysinfo
> > provider that would let you count them all at once.
>
> > Data written to swap or mmap'ped files won't register here, but most
> > heavy writes aren't done with mmap.
>
> Thanks, Dan! Dtrace is really a way to go.
>
> Unfortunately dtrace is not available at 7.0. That means that
> the system should be updated to 7-STABLE.
>
> Are there other possibilities meanwhile?
ktrace -d -i -p 0 ; sleep 10 ; ktrace -C
, then run kdump -m64 and search for large numbers of writes in the output.
"-d -i -p0" selects all current and future children of pid 0, which will
trace all processes. "-m64" limits the I/O dump size to 64 bytes.
--
Dan Nelson
dnelson@allantgroup.com
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