Originally Posted by Thready
I see. I use SyncToy because I only want to sync my photography and important home and work documents between the drives. I use the remaining space on the drives for games. I have about 750 GB of things backed up on all drives and I use 3 TB drives so I have a lot of free space. I have to run the backups manually which I don't like. I wish there were a way for them to automatically back up every time I added new files to the folders.
Actually, you are better off running the backups manually instead of automatically. To be able to back up something automatically, the backup drive has to be kept powered up and connected to the computer at all times. This exposes the backups to infection from viruses and other malware. If you are set up correctly, it takes less than a handful of minutes to connect the backup drive and manually start the backup, then the computer will finish the job without any help from you. When done, just eject, power down, and remove the backup drive, also taking less than a handful of minutes.
I didn't mention any of this at the beginning since you only asked for what we did. While I do not trust Amazon (too many data leaks have occurred there; Backblaze has a much better reputation), you have a fairly solid backup plan in place already. SyncToy has a good reputation and pretty much does the same thing as FreeFileSync. The only things I would suggest is not to set up an automatic backup scheme (you pretty much already have that going with Amazon) and add an offsite backup drive to the onsite backup drive you already have.
While the Amazon backup can serve as your offsite backup, if you had a total loss (computer and onsite backup drive), such as from a fire or theft, it would take forever to download all your data. Having an offsite backup drive would allow you to recover most of your data quickly, then any data you had added or changed since you had last updated the offsite backup can be downloaded from Amazon, which will take far less time than downloading all of it.
I used to use Carbonite but it (and Backblaze) doesn't work with Linux and I plan on switching to Linux in the not too distance future. Also, Carbonite has taken their customer service and tech offshore again (and it plummeted in quality when they did that). I tried Crashplan Small Business Plan, which does work with Linux, but the service was slow and erratic, the GUI sucked, and their customer service and tech help was useless.