I'd use a desktop drive if I were you (powered by a separate mains plug). There's a warning on the back of my Zgemma 2S not to exceed a current load on the USB port and that says to me they've identified it as a possible weakness in the design. I'm using a 2Tb toshiba USB3 I got in a supermarket clearance for £55 and it works well, hotukdeals is worth a look too.
what is it with toshiba lol,i got a 1tb powered to my tm,one thing to double check i use usb for my epg and ext hdd for recordings,somewhere in settings they changed,i spotted it on set up mounts where epg was going to hdd and recordings to 8gb usb lol.
double check if you use both is my warning.
I use a 500 Gb Toshiba 3.0 USB drive, seems ok, haven't had any issues.
I can't get usb to work in Zgemma usb no format option to fat32 tried everything to get this to mount, any help much appreciated