Spindown is a daemon that can spin idle disks down and thus save energy and
improve disk lifetime. It periodically checks for read or written blocks. When
no blocks are read or written the disk is idle. When a disk stays idle long
enough, spindown uses custom command like sg_start or hdparm to spin it down.
It also works with USB disks and hot-swappable disks because it doesn't watch
the device name (hda, sdb, ...), but the device ID. This means that it doesn't
matter if the disk is swapped while the daemon is running.
