Time Machine error - The backup disk is not available - Using internal disk for TM I have an old Mac Pro that I would like to use as a Time Machine server for my small company. I just put in some spare hard drives in the unused bays, and set up a mirrored RAID set to use for Time Machine. I am able to use that RAID set as a Time Machine disk locally for that particular computer, but when I try to use it as a Time Machine disk for a networked computer, I get the error:

Time Machine couldn't complete the backup to "COMPUTER NAME"
The backup disk is not available.


However, I am able to connect to the disk using Cmd + K, or even just by browsing to it from Finder. Is this problem being caused by the fact that I'm using an "internal" disk as my backup disk?

The Time Machine computer is running a newly installed version of Lion (10.7.5) and the computers trying to back up to it are either running 10.7.5 or 10.8.3

Thanks
If you are using the volume directly on the Mac and you are likewise sharing that root folder of that volume, then correct. The hidden time machine files would be problematic.

If you exported a sub-folder on that volume, and placed the necessary Time Machine control files in place, then you should be able to use the exported volume as a time machine volume over the network.