On Wed, 2006-06-07 at 13:07 -0400, Sam Drinkard wrote:
Folks,
At what point in iowait should I start to worry about having abottleneck, or is this something that can't be answerd with a single integer? According to sar, after my last reboot to turn off hyperthreading as a test, at one time, I see 4.9% iowait, but then one minute later, it droped back to 0.01%, and rarely even gets to 1.0%, at least what I remember from yesterday. ?
thanks....
Sam
He-he! The age old conundrum of tuners everywhere. What's appropriate for observed performance X? Of course, first query leaves untold all the things that are needed to get a SWAG (Scientific Wild-Ass Guess).
I/O wait is, of course, a result of many things: HD speed, cache size, bus speed, latency, I/O request rate *and* duration of "flooding" I/O requests, CPU time available to process it..
Given what you mentioned in the "I can't reconcile..." and "swap" threads, I would guess (not knowing your hardware or anymore about your load) that you could sleep well if your peak I/O wait is 4.9% for short periods. If it is usually down at 1% or less, smoke a joint: nothing to worry about!
IMO, in complete ignorance.
Look at other SAR areas to see the things that affect that and you will know if it's reasonable, as in "I really can't do much to improve it and it's too small to justify the effort anyway" or ... not.
Let's see. If you stayed consistently at 4% for 24 hours, should cost you about 57 minutes. From there you can figure if it's worth any effort.
<snippo>
HTH