Date: Wed, 18 Nov 2009 16:06:01 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Steve Bertrand <steve@ibctech.ca> Cc: questions@freebsd.org, Nerius Landys <nlandys@gmail.com> Subject: Re: Measuring disk I/O Message-ID: <20091118220601.GD89004@dan.emsphone.com> In-Reply-To: <4B046D14.1070505@ibctech.ca> References: <560f92640911181259m37d2659w775fa3fafd9499b6@mail.gmail.com> <4B046D14.1070505@ibctech.ca>
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In the last episode (Nov 18), Steve Bertrand said: > Nerius Landys wrote: > > A friend and I are working on a small video-game related project as a > > hobby. We're running several scripts 24/7 that make lots of calls to a > > MySQL database. The mysql server process shows an average CPU use of 1% > > (reported by top) and it never goes above about 2% The tables it's > > hitting are myisam tables. I'm a little bit worried that the mysql > > process is using a lot of disk access. I don't know too much about hard > > disks but my feeling is that too much disk use could slow the machine > > down or cause a premature hard disk failure. WD Raptor model. > > > > I don't know if my concerns are well-founded, but I would like to > > measure impact on the hard disk somehow. I don't know how to see disk > > I/O. I do know how to use top. How do I measure disk I/O? Any other > > thoughts? > > Perhaps gstat(8) will help you get started: > > # gstat -a > > dT: 1.001s w: 1.000s > L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name > 4 176 114 10261 14.9 62 607 25.4 96.8| ar0 > 4 177 115 10389 17.8 62 607 26.5 100.0| ar0.eli > 1 34 34 527 30.8 0 0 0.0 99.1| ar0.elie > 2 66 4 16 20.5 62 607 26.6 98.0| ar0.elif > 1 77 77 9845 12.1 0 0 0.0 93.0| ar0.elig iostat -x gives similar output, although only to the device level, not the slice. There's also top's 'io' mode (press m), which will show per-process i/o stats of varying usability (I/O to zfs doesn't seem to show up). > ...or on ZFS: > > # zpool iostat 1 > > capacity operations bandwidth > pool used avail read write read write > ---------- ----- ----- ----- ----- ----- ----- > storage 1.39T 440G 0 771 0 96.4M > storage 1.39T 440G 0 1.05K 4.42K 126M -- Dan Nelson dnelson@allantgroup.com
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