Wim Decorte of Soliant answers a common question found on forums:
“How can I exclude my externally stored container content from a backup run?”...
If the container data is fairly static and you can exclude it from the backup then you could save roughly 100GB on each backup run and not fill up the hard drive, and that allows you to take and keep more backup sets, right?
Wrong. Well… right of course but the underlying premise is faulty. In the scenario described above, FileMaker Server does NOT actually consume 100GB of disk space for each backup set. FileMaker Server is very clever that way. When it finds a file that has not been changed since the last backup; it just adds a hard link to that file. The effect is easy to observe: run a backup and check the free disk space in Finder / Windows Explorer. Now run a new backup and check the free disk space again. You’ll see that the free disk space was not reduced by the total size of your solution. Magic, right?
FileMaker server is a pretty well written solution, and does plenty of things really well. And FileMaker Server 13 takes it to a higher level, with Perform Script on Server (Psos). And WebDirect. Not to mention Improved Security.
But back to that FileMaker Server backup. Follow the link below to find a white paper by Stephen H. Blackwell and Wim Decorte with lots of details about backups and hard links.