Identifying disk activity

Polytropon freebsd at
Sun Aug 28 05:30:54 UTC 2011

Since I have installed my new system (FreeBSD/i386 8.2-STABLE),
I have found some kind of disk activity I've never had before
on my home system. As this PC is a very cheap product, it doesn't
have a HDD LED. Instead I have to listen to the disk.

This is the strange sound: four groups of short "brrrrt" sounds
within a second, with a short pause between them.

	#####-----#####-----#####-----#####----- = 1 s

This can be heared over several seconds, then silence. From
time to time, a "brrrt" sound appears for 3 seconds in one
long rush.

I am not sure this is related to a program, but I'd like to
find it out. As FreeBSD's I/O subsystem does not work in
real-time, I cannot conclude from actual program file I/O
to physical disk I/O.

Is there a way to force "synchronous disk activity"?

I don't mind if this makes the system run slower, because
it's just for diagnostics, but I'd like file I/O done by
a program to cause immediate disk activity.

My idea is to watch open files and running programs as
precise as possible (as root: "top -St -s 0"). Which
tools (e. g. top, htop, lsof) would you suggest to narrow
down _which_ program is accessing _which_ file, causing
the sound?

I already do suspect Opera (due to opera-linuxplugins-11.50,
linux-f10-flashplugin-10.3r183.5, nspluginwrapper-1.4.4 maybe),
but I'd like to know _where_ exactly this strange sound
came from, as there is no 1:1 relation (running Opera does
not imply the sound to appear).

I have already checked "smartctl -a /dev/ad4" which doesn't
show any malicious behaviour of the disk itself (sometimes
also the reason for strange sounds).

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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