Spindown, as the name suggests is a free opensource command line utility to spin down your disks when no data is read or written of it. This should help save the precious energy and give the disks a longer life. It works by checking the number of blocks read from and written to the disks. When no blocks are read or written to the disk then it is considered idle. When a disk stays idle long enough spindown uses sg_start SCSI scripts to spin the disk down. It also works with usb disks and hotswappable disks because it doesn’t watch the device name (hda, sdb, …), but uses device id.