Cannot create backup in Snapshot

I am attempting to backup my site because I am contemplating migrating it to a new host. I have set up an automatic backup to my WPMU account but it does not run. My suspicion is that the server is timing out before the backup can generate and upload to my account.

What are the optimal server settings to allow this to work? I am getting frustrated with the process and need to generate a backup before anything catastrophic happens. Your help is greatly appreciated.