On Tue, Jan 15, 2008 at 04:57:02PM -0500, Bruce Dawson wrote: > Its been several years (and major kernel versions) since I've played > with iostat, but perhaps my statements here will goad someone with more > recent experience to inject more accurate truths... > > * iostat used to "not work well" on SMP systems.
That's unfortunate. Hopefully that's been fixed. > * your "510kB/s average write on dm-5, but only 184.01kB/s average > write on the enclosing PV?" observation may be due to "write > behinds", caching, and seek/latency optimization. Caching issues was my first thought, but doesn't apply to the 43+ day average numbers in play here. I don't think any of those other optimizations would have such a significant effect over periods this large, either. Eventually all of the data written to the LV needs to be written to the PV, right? > * iostat essentially just does arithmetic on the counters kept by > the kernel. > * For long uptimes, counters can overflow and produce some *really > strange* numbers. I would expect Linux to use 64 bit counters in > recent kernels though. I'd hope there would be some trap to reset all of the counters to 0 if one overflows, but that may just be dreaming on my part. That may be what is happening, though, as the numbers look OK on 10 second intervals. I suppose I'll have to schedule a reboot to get decent numbers. *grumble* > Don't you just love documentation written by developers (I'm referring > to the iostat man page)? I like it, but that's just me. -- [EMAIL PROTECTED] OpenPGP KeyID 0x57C3430B Holder of Past Knowledge CS, O- "I was walking down the street one day when a beautiful bird caught my eye. And I had to climb all the way to the top of a tree to get it back." Abhishek Gami _______________________________________________ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/