which UPS to buy?

rejoyce wrote:
With regards to what actually happens on a power failure, will the ReadyNAS Duo run for a bit and once it detects the UPS is running out of power does it shut itself off gracefully? Is that how it works or what?

Yes. There is section in frontview that lets you configure the setup if you want (system->power, with UPS configuration at the bottom).

Note that if you want you can test the shutdown safely if you like.

You do this by connecting the Duo to regular power, but also connecting the USB cable to the UPS. Then connect something else (perhaps a lighting fixture) into the UPS , and and finally unplug the UPS from the wall outlet. When the UPS battery runs down, the Duo should shut down. If it doesn't for some reason, there is no harm done since the Duo is still running off the main power.