I am using DNN 06.02.05 with 6.1.3 Document Exchange. It was been working great, but recently usage has increased and started to slow down when loading the document view. It's only the initial page request that is slow. When exploring folder and files the AJAX requests are quick. I noticed that the DNN File Manager was also slow for the /Portals/0/DMX folder and found a post about disabling 'Auto Sync File System'. After disabling that option the DNN File Manager performed much better. Could this issue also being impacting DMX? If so, can auto synchronization be disabled?

There are a few other things to consider here as well. Just a few thoughts.

1.) First of all, you want to make sure that at the DotNetNuke level that you have caching set to "Heavy" under Host -> Host Settings as that helps with file system performance.

2.) For the "initial load" time that you mention. Is that the first load for the first user? Or is it the first load for ALL users?

3.) Is your traffic by chance sporadic? If so, the way that ASP.NET works by default applications are unloaded after 20 minutes of inactivity. if you have more than 20 minutes between visits it can add to the time to upload.

As to your question about auto-sync. It is only needed if you are uploading files via FTP to the site. If you are not doing this you are 100% safe to disable.