I have been using an unraid share as a time machine backup for a while now without any problems, using SMB and all the normal settings. All of a sudden, the time machine application stopped seeing my share. No amount of rebooting has made a difference. I tried to create a new Time Machine share and it's also invisible. What might be going on?

 

I'm using 6.8.3 and Catalina (I upgraded from the previous MacOS but that made no difference).

 I can confirm this behavior with at least 2 computers on Catalina. I thought it was something I had somehow borked even though I hadn't changed anything in Unraid. On my server with the TM backups I attempted rolling back from 6.8.3 to .2, to .1, to .0 and rc 9 (in which I know it worked) and still the same.

 

Additionally I created a Tm backup share on my main server and TM did see that disk. I did not connect via the finder but used command+k, added the server location and share name, then clicked connect. That share then populated in the Time machine disk selection.

 

So then I went back to the server hosting the TM backups. I tried the same method but backups failed. Then I noticed the disk had 5gb free on it, the same amount I had specified as the minimum free space. I made more room (166 GB actually) and told TM to backup now. It's currently preparing. So it appears I over-provisioned the disk.

 

This doesn't necessarily address your issue, unless it is not seeing it because of the connection method. I've read that if you mount it as a read/write share via network browsing, TM won't always want to use it. So try the command+k method and see if that helps.

 

Wow, this was exactly the issue! The drive only had 100MB left. As soon as I changed the minimum size the drive reappeared.