'time' for disk io
 

Is there a way of testing the disk i/o of a process like time does for timing?

I know of pidstat but that only works for running processes.

collectl is also cognisant of taskstats and maintains history, try that.
Or maybe blktrace depending on what you really want.

what I have is a 24x7 daemon with heavy i/o.

I have found now that I need to try and limit the disk i/o using my brain.
So I want to try different optimisations.

I have partial data files which I can run "one-shot"
I want to test different iterations and compare the disk stats
on different runs.

If at all possible, try to adjust the algorithms used by a "disk-I/O intensive" process. If not, look hard at cacheing. Hardware purchases are often called for ... caching controllers, faster drives, solid-state.

That's what I am doing all I need is the metrics to prove it! accton looked a good candidate but no disk stats on linux.

I am on a virtual host, off-site, so it's easy to mess about, but can change only at weekends when it's off line, so then I have to sit on it for a week.

I've had some success, I split disk to a double SSD to spread the load and it keeps it generally below the red line but still revs a bit high on occasion for my taste. I will up the CPU this weekend see if more timeslices will help.

Then the boss wants things done and the bloody customers!

This looks interesting
http://jotdownux.blogspot.in/2012/03...ccounting.html

If these are temporary files, then you could set up a ramdisk to hold them.

yes chris, that might do it.


no can't do ramdisk as the data has to be written and I share it over NFS and you can't share ramdisk.


Heart transplant surgery is very easy, it's keeping the patient alive,
that's the trick
;)

one of the tricks with collectl is to run it for awhile or better yet continously and then play back the data with '--top iokb'. to see all the top options try 'collectl --showtopopt' as there are lots of things you can sort by. you can also play back the overall diskio and/or plot it to correlate the two.

only gottcha is to see process i/o stats you need to run collectl as root OR with the processes's uid otherwise collectl can't read the io stats.

-mark