Comment 13 for bug 875719

I would say it is not. The OP on this bug reported that the drive did spin down but then spun back up.

Bug 595138 is a failure of the hdparm scripts to read /etc/hdparm.conf and properly set the spindown option.

To answer Christoph's question, here's a link to how to figure out what is accessing the drive:

http://info4admins.com/tips-to-spindown-your-hard-disk-in-debian-or-ubuntu/