If you do proper backups and are a shell type person, you probably are an rsync user.
In the lowend market, where there is limited RAM available, rsync can really fail in a big way. Failure is out of memory related when rsync attempts to load all the filenames and info in to RAM at startup.
If you are getting out of memory errors and done the search engine researching and swear rsync has a bug, fear not.
This is your new rsync commandline option to postpend to your current script or cron job:
--no-inc-recursive
That cured our ills on a 256MB VPS. Bound to work just as well on smaller instances.