Good article with one fundamental omission…
It doesn’t list network availabillity and server reachability as a con for the online options. That leads to the false conclusion you’re always connected, your network is operating at sufficient speeds, and servers are always reachable. i.e., The Myth of Network Persistence.
Online backups are useful but you also can’t ignore or be unaware of those variables.
The bigger the better for Time Machine. It means that it can store more historical versions, and retain deleted info for longer. You could use an 8TB drive for a 256gb internal, it would just give you more options for restore and longer retentions. TM backs up any changed files (not the whole disk) on an hourly basis, and then retains for a sliding scale hourly for the first 24 hours, daily for the next month, then weekly and then monthly.
CCC AND SD clone your drive, I.e. a direct copy of that drive at that time the backup runs. I’m unsure whether you can have multiple images on the same drive, but a failure of that drive could lose all images if you can, so probably better not to.
Questions are fine. 
I’ve used Time Machine for years and we also advocate it since it’s free, built-in, and simple to use. That doesn’t mean it’s perfect but it’s generally very good and absolutely better than no backups at all. (Don’t get me started! 
)
That being said, I’m about to pony up for Carbon Copy Cloner as I used it this weekend to archive a 95GB and a 35GB user acccount. Simple to use UI with more advanced functions available. And impressively fast.
Plus… backups are what Bombich and company do! If you want to really nerd out, check out their FAQ, support, etc. If anyone knowns backups inside and out, I’d say it’s these people 
I’m technically unsure as well as I’m just now using CCC, but partitioning a larger drive for each machine you’re backing up would likely work.
This is a very well written book that might help [Take Control of Backing Up Your Mac(https://www.takecontrolbooks.com/backing-up/)
This CCC knowledgebase article is helpful in the context.
I certainly agree with that. The knowledgebase is a mine of information.
I’ve used CCC for years and am sure you won’t be disappointed with it.
Stephen
It will work but as @geoffaire pointed out it’s not really a great idea. Drives are cheap compared to losing your data and/or backups.
No.
Encryption is an option, i.e. not required. Unfortunately the process of encrypting the disc adds even more time to the initial backup.
Encrypted and bootable backups with CCC (and SuperDuper?) require a bit of fussing for the initial backup. I don’t bother with making my clone backups bootable anymore but wouldn’t dream of not encrypted any backup. Also, latest (ARM-based) Macs make it very difficult, if not impossible, to create bootable backups, unless things changed over the past couple of months. My understanding is that bootable backups will likely be a thing of the past, which is too bad.
I think that’s no longer the case when you use APFS on your backup drive (someone please correct me if I’m wrong). In times past there was a way around the initial encryption time too, but it wasn’t quite as simple as checking the “Encrypt backup” button in the TimeMachine control panel.
I’m surprised that nobody has “called you out” on this, but the “cloud” is not a backup. If you accidentally delete or mangle you local copy, the one in the cloud gets deleted or mangled as well. A backup allows you to go back in time and restore your file from before the catastrophe.
This makes sense. The way I’m approaching it is using hazel to backup my cloud storage in another cloud storage
A case in point:
Second time this week.
Yeah, my experience with TimeMachine is that it’s been very, very reliable when the backup drive is directly attached, and far less so when it’s over a network, especially a wireles network.
Well, when this Time Capsule (bought the day after Apple announced in 2018 they would stop making them) bites the big one, I’ll have to go “direct-connect,” too.
Time Machine is great when it works, but a real pain when it doesn’t. It’s nice as a built-in that is quick and easy. There was a pretty good website pondini.org but it looks like it’s gone. Somebody saved a copy at Time Machine - Frequently Asked Questions 1. How big a drive do I need for Time Machine? This should answer your question about drive size.
Arq backup https://www.arqbackup.com/ - I’m surprised that nobody has mentioned arq yet. It’s a solid alternative to time machine. This is the primary software that I use to backup to local, external hard drives, and cloud destinations. Highly recommended!
Clone/bootable backups - I believe the three most popular are Super Duper, ChronoSync, and Carbon Copy Cloner. I believe in having a bootable backup because if the internal drive on your mac goes bad, then you can immediately use the bootable backup. It doesn’t require any type of restore function.
Can you still boot an M1 Mac if its internal drive is bad? Seems like we’re still sorting this out.
Not according to this.
Good point. Pre-m1 it made sense to have a bootable backup. Does anybody know if you can create a bootable backup on an external, and then duplicate that to a new internal drive if the old internal drive fails?
I love the idea of having a replacement that gives you minimal downtime.
OS install + Migration Assistant is probably your best bet. If you can make a business case for having to cut your recovery time by 2 hours then you can probably make the business case for having second computer that you can fall back on, on which all your data is available. Not that I’m trying to give you a reason to buy another computer or anything
Given that the jury is out whether this is even possible on an M1, this advice may not even matter.
But if you CAN boot an external drive, you really want an SSD. There’s no rule that it has to be, but a 500 GB SSD will probably only set you back $60-$70 (watch for sales).
The reason an SSD is preferable is because someday you’re going to be booting the operating system off this thing, and a spinning disk on the other end of a USB cable is very, very slow.
Worth the little bit of extra outlay for the SSD if you’re going the “bootable backup” route.