Where shall I put my (Condor) log files?

As always, the correct answer is: It depends.

You can put your log files in your home, e.g. assuming your user name is MYUSER that would be /home/MYUSER. This has the benefit that all nodes can see your log files (if they need to) and these log files are automatically put into backup (on Atlas). However, this approach can slow down the Condor daemons on the submit host as they have to have access to the log files very often and doing this via NFS is a relatively slow way.

One solution is putting the log files under /local/user/MYUSER which mitigates the NFS issue, but this might be problematic if your compute jobs need to access these files (still possible but you have to take care to use the correct paths).

Our suggestion here to use the following path (assuming you are on submit machine atlasX): Put your log files under /atlas/user/atlasX/MYUSER as this is guaranteed to be the same path on any node, every node can access this area via NFS and on the submit host atlasX this gets automatically converted into a local mount, i.e. you get around the NFS overhead.