[Suggested New Feature] Time Machine-style backups
I would like Acronis True Image to back up my Windows files in the same way as Mac OS backs up its files with Time Machine. The benefit of this is that there would no longer be any need to worry about "full" / "incremental" / "differential" backups or full backup disks; if the disk fills up, it can remove the oldest backups until there's enough space to continue.
The way that Time Machine does this is by using "hard links" (see https://en.wikipedia.org/wiki/Hard_link), which means that a single file can exist in many places and it keeps track of the number of hard links to it. Deleting a hard link does not actually delete the file unless the file has no remaining hard links.
Time Machine works by starting with a full backup of the disk. Every subsequent backup only contains changed files; unchanged files are hard-linked to the copy in the previous backup. If you delete an entire snapshot from a backup, then any file versions not unique to this backup get their hard link count decremented by one, but they still exist for the other backups which reference them.
Not all filesystems support hard links (specifically, network filesystems often don't), so Mac OS creates a filesystem inside a container that it puts onto the network drive.
The benefits of this kind of backup are:
- No more than one "full backup", ever - all subsequent backups are incremental; this means less time and less wear on the backup drive
- You can delete any backup snapshot (earliest, latest, or anywhere in-between) without corrupting other snapshots
- No need to limit the size or age of a backup; it can continue growing until it's out of disk space, at which time the oldest backup can be deleted, repeat until there's enough free space
- A hard drive can be restored from any snapshot of a backup