I would start with a small sync folder, if there is a major issue it should be already obvious and because of a few files, the logs are much smaller and the error easier to spot. For the Linux logfiles, you can use any text editor you want. What can be useful is the tail -f /path/to/logfile command which shows you in realtime all the new entries in the file.
Here some starting points for logfiles:
https://help.ubuntu.com/community/LinuxLogFiles