AeroFS automatically saves a local copy of a file every time it receives an updated copy of that file from a peer. This is true whether you receive a file update from one of your own devices, or one from another user in a shared folder.
We call this Sync History, and it provides a simple protection plan against mistakes.
Suppose you delete a file on your laptop. AeroFS will synchronize that change - in other words, delete that file on all your devices. If the deletion was accidental, you will probably not be happy about this synchronization.
The same is true if something bad happened to the contents of a file (say you replaced the text of your thesis with a long string of "All work and no play...")
What Sync History Is Not
Sync History only makes local copies when peers copy to each other, and we will automatically prune old copies (or prune newer copies to save space). It is not meant as a substitute for version control systems. And you should be aware that local changes will never be copied into Sync History if they are not synced to a peer.
Where is Sync History
The Sync History dialog is accessible through your AeroFS client - click on the AeroFS icon in the taskbar to bring up the menu and select "Sync History..."
From there you can look at old versions and clean up old copies or "promote" the old versions to replace the current copy.
Disabling sync history
The AeroFS Preferences pane lets you disable sync history on an individual device.
Given the description above, why would anyone want this?
Some people have existing backup software for the files that AeroFS is syncing.
Some people have huge data files, and the cost of keeping old copies around for those is just too high.
Some people use AeroFS on devices with very little local storage, and want to disable Sync History only on those devices.
So, you might have a good reason to disable Sync History, but please take care.
By the way, if you disable Sync History it will not affect how we handle conflicts on your files! Any conflict will still be saved and you will get a choice of how to resolve it.