[Discuss] How can you tell which application exercises the disk a lot?

[Alan W. Irwin]

On 2007-11-03 16:57-0700 Alan W. Irwin wrote:

> Has anybody else here experienced the disk light for their Linux box
> going on every two seconds?  That does not happen for my two older boxes.

Finally nailed what was doing this by doing selective install and uninstall
of packages and metapackages.  "apt-get autoremove" is your friend for
removing whole swathes of packages that were installed using one
metapackage. It turns out the hal package (hardware abstraction layer) runs
a daemon called hald.  Whenever that daemon has been stopped the disk
activity light quits blinking.  Whenever it is started again, the blinking
starts again.  This is for Debian testing.  For a substantially older Ubuntu
Dapper system which runs the hald daemon, no such two-second disk activity
is noticed but probably that older hal didn't have the capabilities that the
current hal has.  (Or from http://en.wikipedia.org/wiki/HAL_9000 perhaps
that package should be called HAL. :-) )

Now hal is an really important package with lots of other packages that depend
upon it so I am stuck with it if I want to run any desktop.  And I assume hald
is important to hal to obtain the information that is needed about hardware
that is connected to your system.  So the hald daemon has to be run, and
I am stuck with the disk light activity blinking every two seconds.

What I expect is going on is that hald is interrogating the SATA bus every
two seconds to sense what disks are attached, and that is showing up on the
HDD LED lights as "disk activity" (at least for my current ASUS PK5-V MB).
>From the iostat and vmstat numbers there doesn't appear to be any actual
mechanical motion of the disk so this sensing should not wear it out. On the
case used for my new PC, the HDD LED is a rather bright red light so you
really notice when it is blinking every two seconds, but I can live with
that so long as no actual reads or writes are going on.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
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Linux-powered Science
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