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Old 04-18-2014, 12:05 AM   #1
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high i/o utilization on file systems

Hi ,

Am using "fuser -cu /myfs" to identify the process accessing the filesystem /myfs . But i want to list the process which are consuming high i/o on this disk . Is there a way to use "iostat" and "ps" to find out the process consuming high io on this particular Filesystem?
Old 04-18-2014, 05:15 PM   #2
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Collectl can help.

any post by Mark Seger is a "keeper" on this subject.

Hi Mark!
Old 04-18-2014, 06:34 PM   #3
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That'll make his (Mark) Easter break better

In his case maybe not - I don't believe the taskstats as maintained by the kernel are device/partition specific. The OP can get this sort of data from blktrace, but needs some setup, and post-processing. Initially was at the block device level only, but can now be specified for partitions.
Old 04-21-2014, 03:24 PM   #4
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Trying to pin a specific process to a disk can be a problem as collectl doesn't track that sort of thing, however sometimes you can infer a lot by correlating various things. So assuming you have a bunch of raw collectl data. It's pretty easy to see how busy a particular disk is with 'collectl -p filename -sD --dskfilt xxx -oT' noting the oT will stick a timestamp on each line. If you can identify some spikes you think might be attributed to the problem process, this is a good thing. Be sure to note the timeframe.

Now if you play back the same data and report process I/O usage with 'collectl -p filename -sZ --from hh:mm-hh:mm --procanalyze', this will report a summary of the processes that were running between those two times in space-separated format, which you can then load into a spreadsheet and from there you can identify which processes were doing a lot of disk i/o. Keep be mind this will not tell you who was talking to what disk, only that they were doing I/O. This may give you the answer you're looking for and maybe it won't.

The other thing is if the spikes are relatively short, the 1 minute default process monitoring interval may be too long to see anything and running collectl with the a 10 second interval like the disk processing interval, may be more helpful.

No promises this will work for you but it's he best I can come up with at the moment.

good luck

Old 04-22-2014, 12:42 AM   #5
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Thanks for your replies .

vmstat shows very high IO utilization on this mount /myfs. am looking for those processes which is causing the high IO to this mount and what are the files being accessed(both on read and write). Yes, post-processing is must here to analyze.

I cannot go with collectl on this particular environment . Any suggestion to collect the ps consuming more i/o on this live system?
Old 04-22-2014, 03:45 PM   #6
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Could you say more about why you can't go with collectl? if you don't have privileges and so can't install it as root, you can always grab the tarball and just extract collectl into you home directory tree and run it from there.


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