Ok maybe you're right. But I tried a couple of different devices, also a fresh installation of the newest build of FreeNas 8.
What devices are qualified? Is there a HCL somewhere?
And maybe I'm not caring about my data in the end. Or maybe I am, because well, at this time I cannot backup. Since Lion upgrade, that is.
The official documentation used to say that the only supported network backup destinations were the internal drive of a Time Capsule and a Mac AFP server running Mac OS 10.5.8 or later. That seems to have been changed, and now it says that only the devices shown in the TM preference pane (without hacking the AppleShareClient preference file) are supported:
There also used to be a technical article on the requirements for a TM server, but that seems to be gone or moved. FreeNAS would have netatalk as its AFP implementation, and that certainly won't work.