How do you guys deal with deduplication?

Say, I back up the home directory in my computer to a NAS. The computer dies at some point. I get a new computer and recover home from a backup (or part of data in the home directory). New data is added to the home directory. New computer is backed up to NAS. Over time, most of the data in backups are the same.

Any idea how to deduplicate, or avoid this problem?