MPG strongly recommends clone backups as a “real backup”. TimeMachine withreally a toy that is good for a few days (and quite useful in that regards). The “toy” comment might seem unfair or even outrageous, but history proves is perhaps too complementary. More on that below.
Which is why something like a 4-bay OWC Thunderbay 4 in a non-RAID configuration* is so useful: one drive can be for Time Machine and another can be for a clone backup. I call these “half backups” because if the computer is eaten by aliens or burns up in a fire or is stolen, always-attached backup drives have zero value. Keep separate external (away from the computer) as your #1 priority of course. Both are ideal so that backups happen every day and the offsite backups for Plan B for the worst-case scenario.
* RAID is NOT a Backup nor is it advisable to use RAID for backups, excepting only certains specialized situations.
Time machine failing?
A May 13 post I came across macOS Sierra bug not fixed: Time Machine backups still stop working seems eerily familiar with troubles reported here on MPG back in 2012. A bit different, but the same bitter pill.
The old bug in macOS Sierra, which has been present since its first release last year, resulting in Time Machine backups and other background tasks becoming highly irregular and unreliable, has not been fixed in Sierra 10.12.4.
After a variable period of continuous running, usually longer than 7 days, sometimes over 30 days, Time Machine backups and other activities which are managed and dispatched by the Duet Activity Scheduler (DAS) will cease being scheduled correctly. They then become extremely irregular and unreliable – backups may be made several hours apart, for example. All activities managed by DAS are affected.
Besides ceasing to operate entirely or partially, there have been crashes in Time Machine and a variety of other problems that MPG has seen over the years. Hence my “toy” comment with respect to Time Machine: backup software has to be rock solid, both for backing up and restoring. MPG recommends Time Machine, but ONLY as an adjunct for a few days or few weeks—max.