I moved PostgreSQL on the home server gosper from an install I compiled myself ages ago to the debian-maintained package. As a side-effect the data moved from /scratch to /var which is on a different physical disk. Now the disk with /scratch and /boot has no reason to stay awake all the time and it spins down, saving another bit of power. Quite visible in the UPS stats. I guess splitting OS and lesser-used data disks in a home server can save a bit of power. The assorted sensors at home overview shows disk hda sleeping a lot more.
As a side effect the postgresql data is now also included in the backups. The database at home went from a few tables with copies of data from webprojects I was developing to data actually in use. Time for backups.