All of the current (plain) Reds are SMR (shingled magnetic recording) drives and in most opinions should be avoided.
I don't want to start an argument, but I did read the articles, Randy, and I think I would change that sentence to add "in RAID arrays" at the end, just to be more precise. That is what the articles complained about, that when you use one of these SMR drives in resilvering a busy RAID array (adding a new drive), it has a tendency to fail in the integration, probably because of the write speed being slow. None of the articles said that single SMR drive, by itself, in a backup scenario for a home user has major failures. Slow? Yes, but in a home use for backup, I think slow is acceptable. It's a backup, after all. I've been using slow drives for backups for years, it's a good use for them. I do agree that slow drives, in a highly volatile data environment, are a real problem, but for backups in a relatively stable home use case, they can work pretty well.
Now, a bootable clone, where I plan to run my system from the drive? That needs a good, speedy drive, probably an SSD instead of RDHD. But the use-case there is different.
Bombich also derides the SMR tech, but offers no proof or evidence of any real issues. His statement was:
We anticipate considerably worse performance for APFS in particular on these devices.
"Anticipating" performance issues is not "experiencing" them. His argument would have been more potent with some citation of actual issues. For example, if people were complaining to him about real-world issues, he could have, and should have, cited those issues. Or if he, himself, had actually tested CCC on SMR drives and had some statistics, that would have been more compelling. Even saying something like "I would tested and can say that a backup to an SMR drive would be X% slower than to a standard drive" would have been useful.
Is there any article with comparison figures for an SMR drive in a home use environment? Something that turns anticipation into experiencing? That would be handy to have as we make statements about drives.
That said, I have been avoiding WD recently, despite my previous success with them over the years, because they have started to use a proprietary interface from USB to whatever the are using for the drives themselves. That technology means that if a WD External fails, not because the drive itself has issues, but because of this proprietary interface, the drive cannot be moved to a new non-WD enclosure and then work to be recovered. Found that out the hard way when one died on me and when I opened the case saw the non-standard connections. Fortunately, I had another WD drive where the drive had failed but the interface seemed to work, so I made a Frankenstein of them and got my data off the drive and onto another. So, no more WD drives for me now.
