This is by far the best Mac-only, space-saving, technically sound, reliable backup software out there, hands down. It's a shame that it seemingly receives so little attention in reviews, way less than it deserves.
I use it automated and regularly to keep rolling and staged backups of my main work computers (Mac Pro, Mac mini and a MacBook Pro), and it has so far never lost any data, but saved my butt already several times.
It is software whose function of restoring accidentally deleted or gotten corrupt data you usually use seldomly, but it has been an economical bargain for me in only those five crusial instances I depended on it in the last 8 years.
Unique features I use and that sets it apart from Time Machine and many other solutions:
• Machine keys: Use a machine key to store data from several Macs into a single archive. The logic in QRecall ensures that identical data is only stored once(!) in the archive (e.g. fonts, OS files, applications). In fact, my archive of two machines' startup volumes (each having about 1.5 TB of data on them) for a staged backlog of 2 years (30 days each back from now, then bi-weekly, then monthly layers) is only 2.3 TB in total!
• automated, scheduled backups, almost not noticeable when working simultaneously on the machine
• sophisticated inclusion/exclusion rules
• automated compacting and rolling merge of backup layers (points in time) in the background,
• excellent, personal support by the developer
• extremely high precautions and consistency checking of the valuable data bay way of clever algorithm design
• efficient repair routines in case of hardware defects on the archive target media, network interruptions or power outages
• minimization of storage data usage by detecting duplicate data blocks and storing only a single instance of them
I am depending on this software now for over 8 years (with 3 machine keys purchased), and it has never let me down. Highly recommended!