I have 3 hard disks in SATA-to-eSATA external enclosure which I occasionally need to plug to perform backups and to unplug when done. I found it annoying to have to restart the whole computer at every turn, especially when SATA is supposed to bring hotplug abilities. If you mainboard / SATA chipset and disks support hot plugging and unplugging, you can do this by following those instructions.