Identifying disk activity

[Warren Block]

On Sun, 28 Aug 2011, Polytropon wrote:

> 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.

That could be a "t-cal", thermal calibration.  Depends on the age and 
model of the drive, some drives don't do it.  Could be other internal 
drive activity.  WD drives like to park heads often, loudly, and for no 
good reason.

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

Turning off soft updates will help, but not make disk writes 
totally synchronous.