Looks like several months since we've had a topic with "backup" in it, so...
Please hurry down to your local interweb outlet and pick up a copy of TidBITS (the just published
#1468 edition). There is an article discussing changes to CrashPlan (which no longer offers a consumer version, BTW). There are some very interesting details about what really gets backed up and how. Please read the entire report which also includes statements from Backblaze. For those unwilling to take the time, here is one of the most significant paragraphs from
the article:
[R]emember, an Internet backup service is only one part of a solid* backup strategy, and it should always be seen as the backup of last resort, the one you turn to if everything else is lost. Spending a little time reinstalling macOS and downloading apps isn’t the end of the world—losing your actual data is.
So whether you’re using Backblaze or CrashPlan or some other Internet backup service, always make sure that you also have a local versioned backup made by something like Time Machine and a bootable duplicate created by something like SuperDuper, Carbon Copy Cloner, or Chronosync. The versioned backup lets you recover an older version of a file that became corrupted or was damaged by human error and then saved, and the bootable duplicate enables you to get up and running as quickly as possible if your entire drive dies.
For more "complete backup advice, see Joe Kissell’s
Take Control of Backing Up Your Mac, Third Edition".
* In my opinion, an Internet backup service is mandatory for any business. It might be more of a luxury for most of us "consumers", unless we intend to profit from our computer-based work. The point is,
backup, BACKUP, B A C K U P ! ! !