@Kevin_Z  OK well I hope they are going to send me a hard drive to plug into it, because I broke the one I used before by having it plugged in. 

Also I hope there's a detailed guide they will send me, that they themselves have tested.

@jerclarke Sounds like the drive failed. Are you suggesting that the router may have caused unusual wear-and-tear on the drive that caused it to fail?

I just ordered a USB drive that I'm hoping to be able use on my C2300 Archer, as a replacement for my old Time Capsule ... best case, it actually works, if not hopefully I can just use the drive via USB ... but if it's going to kill the new drive ...

@RayZ I can't prove anything, and I gave up after the backup stopped backing up because I couldn't bear to do the whole cycle of getting a fresh backup set up. 

What I know is that like I said, it was spinning constantly while plugged in, like it was copying files rather than just sitting there, and then it didn't work properly when I reformatted it on my laptop (Time Machine refused it). I bought a nice new drive and am just plugging it in every day when my computer is at my desk, and I am not eager to plug it into the router and find out what happens. 

Backups have to be reliable, that's their job. The one I had on the Archer barely lasted a month before it stopped working with Time Machine (and it was 2TB backing up a 1TB laptop FWIW). 

I'm waiting for someone else to say it's working for them before I risk another disk on the system. 

@jerclarke Well, first attempt is not looking good.

I formatted the drive as "Mac OS Extended (journaled)" and was able to get it set up, the backup started and I left it overnight. It backed up over 300 GB and then stopped with "An error occurred while copying files."  Now every time I try again I get an error:

Time Machine could not complete the backup to "ArcherC2300.local"

An error occurred while copying files.

Fortunately, the drive still appears functional as a USB drive. Did we ever get an answer about what format to use for the drive?

I think I'll start over and give it another try. I'd be happy for any pointers from TP-Link about getting this working.

@jerclarke This time I'm trying it using NTFS file system, since that's what was suggested by @Kevin_Z in #12 in this thread. Obviously, the file system used inside the sparsebundle will still be Mac OS Extended (journaled), but maybe the router's NTFS disk drivers are more reliable than the Mac OS Extended ones. Backup has started, we'll see how it goes.

@RayZ if what you want is to get a single back up finished, my biggest recommendation is to use the exclusion list in the time machine settings to remove everything but your basic user directory. Specifically get rid of whatever directories are taking up hundreds of gigs. Once the initial backup is finished with the exclusions, you can go back turn off the exclusions and do a fresh back up to add them.

This will let you at least see if finishing a back up as possible and if updating that backup as possible.

Sadly one of the effects of the recent updates to time machine is that it's extremely ambiguous about what has and hasn't been backed up and what your status is. Doing it incrementally by having exclusions for your big directories to start let's see you at least have a sense of your progress, and get to that point where it's "finished" at least partially. 

@jerclarke I saw that suggestion earlier in the thread, so that's what I did. It was successful with the NTFS formatted USB drive attached. In fact, I was able to add the excluded directories back in and that finished and it has done numerous hourly backups since ... probably 900 GB +. Right now I'm in the middle of backup up another Mac (another 900 GB or so).

So it looks like it's working at the moment and the speed is better than I expected. Now we'll just have to see how reliable it is over time.

Btw, correction to my previous message ... I think the format of the sparsebundle created by Time Machine is now APFS (Case-sensitive)

@jerclarke, just wanted to check back in to say that things are still working fine after several weeks with two Macs backing up to a cheap portable USB drive formatted as NTFS plugged in to my TP-Link AC2300.

@RayZ 

Has anyone ever done a full recovery using a drive backed up this way? 

I have been burned in the past thinking I had a good backup and did not.