USB drive spins up every hour

[Stefan Monnier <monnier@iro.umontreal.ca>]

My USB-connected drive spins up every hour (or even half-hour).

This is a serious problem since it's a 3.5" drive, it's almost always
idle (I only use it once a day for backups) and it's not in a place
where I can easily plug it in and out.

Googling, I found a very similar looking problem that occurred a few
years ago in libatasmart and which caused DeviceKit to spin up the
drives every hour or so.  But I have no DeviceKit here (running Debian
testing).

Using /proc/sys/vm/block_dump tells me that there is no disk activity
that justifies spinning up.
I have smartmontools installed, but "ps auxw|grep smart" confirms smartd
is not running.
There is no `cron' activity around the time the disk spins up either,
not anything disk-related in the logs.

Any idea what it might be and how to find out and fix it?


        Stefan