I’ve been struggling for the last 18 months trying to get Time Machine to work with disks attached to my Airport Extreme Base Station (AEBS). Things would work once or twice then stop. Disks would disappear and reappear. Arrg! At this point I should say that external disks on AEBS are not officially supported as targets for Time Machine, so the fact that it doesn’t work is not surprising but very frustrating.
The Apple Time Capsule is supported, but as I have a 4TB Drobo disk array and a new dual-band AEBS I don’t see the point of going out and spending $299 and up for yet another device. Despite many attempts at different fixes nothing would work. Ultimately I gave up.
Then a couple of days ago whilst troubleshooting another problem I came across a post in a forum that suggested enabling an option called ‘Use Interference Robustness’. On the AEBS, choose “manual setup, the Airport pane, Wireless tab, ‘Wireless Options’.
This innocuous little check box seems to have worked miracles. Since I turned the option on I haven’t noticed any speed degradation on the network, and Time Machine has been working flawlessly! I’m now three days into the new setup and monitoring it closely. The big test is going to be a restore (backups are useless if they won’t restore). Keep watching this space for an update.