Disk power-down not possible

[Peter Ganzhorn]

Hi,

I've tried to save some power with my laptop by powering down my disk 
via "hdparm -y /dev/sda". The disk stops spinning immediately but will 
start up within 5 seconds or less.
To find out what's keeping the disk busy I got me blktrace and blkparse 
and it seems the following processes keep the disk busy all the time:

swapper
pdflush
xfssyncd
xfsbufd

Is there any way to suspend those processes if I want to power down my disk?

Peter