dtrace discuss - Feb 2008 - DTrace script to find who''s accessing my disk

Is there a dtrace script usable by novices (i.e., me) that will help
me figure out which process is accessing my disk every 3 seconds?

I moved my home directory to an external disk and now I can hear the
disk rattle every 3 seconds.  It''s driving me crazy!  I really want
to find the culprit.

I found the DTraceToolkit and used the iofileb.d script, which is
pretty close, but according to it there were no accesses to files
on the disk I''m watching.  That seems wrong.  Really I''d like
to get
a trace as the accesses are happening, not a summary at the end.

(BTW, any chance it''s zfs itself accessing the disk?)

Thanks.

iosnoop in the dtracetoolkit... :)

Bill Shannon wrote:
> Is there a dtrace script usable by novices (i.e., me) that will help
> me figure out which process is accessing my disk every 3 seconds?
> 
> I moved my home directory to an external disk and now I can hear the
> disk rattle every 3 seconds.  It''s driving me crazy!  I really
want
> to find the culprit.
> 
> I found the DTraceToolkit and used the iofileb.d script, which is
> pretty close, but according to it there were no accesses to files
> on the disk I''m watching.  That seems wrong.  Really I''d
like to get
> a trace as the accesses are happening, not a summary at the end.
> 
> (BTW, any chance it''s zfs itself accessing the disk?)
> 
> Thanks.
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org

Hey Bill,

Take a look at /usr/demo/dtrace/iosnoop.d on your system. It''s an
example
which comes straight out of the chapter in the Solaris Dynamic Tracing Guide
on the io provider:

  http://wikis.sun.com/display/DTrace/io+Provider

Adam

On Wed, Feb 27, 2008 at 05:46:11PM -0800, Bill Shannon
wrote:
> Is there a dtrace script usable by novices (i.e., me) that will help
> me figure out which process is accessing my disk every 3 seconds?
> 
> I moved my home directory to an external disk and now I can hear the
> disk rattle every 3 seconds.  It''s driving me crazy!  I really
want
> to find the culprit.
> 
> I found the DTraceToolkit and used the iofileb.d script, which is
> pretty close, but according to it there were no accesses to files
> on the disk I''m watching.  That seems wrong.  Really I''d
like to get
> a trace as the accesses are happening, not a summary at the end.
> 
> (BTW, any chance it''s zfs itself accessing the disk?)
> 
> Thanks.
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org
-- 
Adam Leventhal, Fishworks                        http://blogs.sun.com/ahl

On Wed, Feb 27, 2008 at 05:46:11PM -0800, Bill Shannon
wrote:
> Is there a dtrace script usable by novices (i.e., me) that will help
> me figure out which process is accessing my disk every 3 seconds?
> 
> I moved my home directory to an external disk and now I can hear the
> disk rattle every 3 seconds.  It''s driving me crazy!  I really
want
> to find the culprit.
> 
> I found the DTraceToolkit and used the iofileb.d script, which is
> pretty close, but according to it there were no accesses to files
> on the disk I''m watching.  That seems wrong.  Really I''d
like to get
> a trace as the accesses are happening, not a summary at the end.
> 
> (BTW, any chance it''s zfs itself accessing the disk?)
> 
> Thanks.
# dtrace -n ''io:::start{@a[execname]=count()}''

Wait a minute, and then hit ctrl-C for a summary.  If you want
individual traces you can start with
 
# dtrace -qn io:::start''{printf("%s\n", execname);}''

or add execname tracing to /usr/demo/dtrace/iosnoop.d

of course you will see sched (zfs, pageout) waking up
and doing chunks on a regular basis, but not every 3 secs.

If you suspect a kernel issue you can aggregate by stack().

-Mike

-- 
Mike Shapiro, Solaris Kernel Development. blogs.sun.com/mws/

Nathan Kroenert wrote:
> iosnoop in the dtracetoolkit... :)
Ah ha!  (I should''ve looked harder.)

Now if only I could figure out why my disk is making noise every
3 seconds even though no processes are accessing the disk.  Should
iosnoop see activity unrelated to any process?