Using Time Machine to back up multiple SSDs to one single SSD

By default, Time Machine backs up every MacOS-format drive connected to your computer that is not a backup destination drive and is NOT on the exclusion list. It makes one full backup initially, then about hourly adds incremental changes. Over time, when space gets tight, it consolidates old backups when possible.

As long as your two 2TB drives are not on the exclusion list (your screenshot shows them on the exclusion list) they will be backed up, PROVIDED they are in one of several MacOS formats, such as {APFS or MacOS extended}. Recent MacOS favors APFS source drives, but allows MacOS Extended source drives.

'Final Cut Libraries' appears to be APFS format because it has a container-disk inside.

You have not said what format your 'Video' drive is, but it does NOT appear to have a container disk inside. IF it is MacOS extended format aka HFS+, it does not need to be reformatted right now, but will be faster in daily use if you did reformat.

Drives in Windows New Technology File System (NTFS) can NOT be backed up because the data structures required to note 'what folders recently changed' can not be created there.

Ideal size for a backup drive is about 2.5 times the size of the data that needs to be saved. Smaller drives can be used, but will become tiresome as they get filled up. Time machine works at low priority in the background, so as not to derail your important work. Therefore, there is no additional benefit to a drive that is fast. Choose Bigger over faster.

You can ADD and additional backup drive at any time, and Time machine will create an additional stand-alone backup set on any additional drive(s). Every-other backup goes to every-other drive, and either drive can be removed at any time..

The annotated graphic with red arrows: what are you trying to show?

The two external drives total almost 2TB of used space. 88GB does not seem to be related to the 3 external drives in any way.

I think the answer to OP’s question is much simpler than made out: remove the two 2TB drives from the exclusion list.

Once Time Machine is finished backup both drives to another 4TB drive without Time Machine (after adding it to the Time Machine exclusion list) so two backup strategies are in place.

Then, if desired, reformat the video SSD as APFS and copy the video files back from the second backup.

I think you just need to remove the two 2TB drives from the exclusion list.

"Here is a screenshot using Disk Utility...It seems there is enough space?"

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I see.

So, what you need to do is format these drives to APFS. Name it what you like. Use APFS for the File System. So, extract what need be so that no data is lost, and then format the drives anew by erasing them in Disk Utility. Create the Time Machine Backups from there: If you need to create a new backup from Mac - Apple Support

"As I tried to explain, the (2) 2 TB drives are not full (Final Cut and Video). The 4TB drive (Back Up Drive) is brand new.[...]"

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About Time Machine Backup:

A. What is Backed Up:

Time Machine Backup is for your entire Mac. You cannot just backup particular files with Time Machine Backup.

B. These are Excluded Drives:

All three drive are being listened in this "Exclude these items from backups:" list.

C. View the Consumed Storage in Disk Utility:

So, how large is your internal hard drive? View it in Disk Utility, and see what it mentions for used space. You may be taking up too much space --period.

Creator_needs_help Said:

"I see now too!!: Thank you so much - I will be very careful to make sure I keep those files on say another SSD while I reformat the others and go through and make a new Time Machine backup. Whew! Sometimes these things are just way harder than they need to be. Thank you again!"

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You are welcome!

Excellent job troubleshooting!

ghr165 Said:

"If this is still your aim then I don’t understand the accepted answer. Why are the 2TBs being reformatted?"

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Apple Recommends you Wipe the Disk Clean:

You are creating one volume.

1. Go Here: Types of Disks you can Use with Time Machine on Mac - Apple Support
2. As it Reads: "The entire APFS volume is reserved for Time Machine backups."

ghr165 Said:

"But there is one new 4TB disk to be used for Time Machine. : Why reformat the two 2TBs?"

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Why to Format All of these Anew:

When macOS High Sierra was released, APFS became the format to use. You'd use these drives as desired. As an example, you'd use all but one for external data storage and data transfer. The standalone one you'd use for Time Machine Backups --it's your call. Migrate the data back in to the drive, once all the formatting is complete.

Apple recommends you format all drives anew directly after purchase, when using them with a Mac. Using the internal software, data can become intermingled between macOS and other Operating Systems. I format them all anew when purchased, and it takes just a few seconds. It just makes it all cleaned out for Apple device-only usage.

Based on personal experience...

As a Side Note: Consider purchasing data recovery protection plans with these, as a way to get the drive serviced, incase it fails or it corrodes(for whatever reason).

Creator_needs_help Said:

"Using Time Machine to back up multiple SSDs to one single SSD: I was researching and trying to find an 8-16 TB SSD with a data recovery protection plan as you recommended. (Thank you btw!)"

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You are welcome.

Merging these Two Drives:

A TMB is no more than a file, officially. You could export them all to another drive for archival purposes --a wise thing to do, if you need to get data back some day.

What I Strongly Recommend:

Backup Plus Portable 5TB HDD by Seagate. You'd format it in Disk Utility, making is of APFS format. Then, use it for backing up your computer's drive. Just know that if you choose to encrypt it, that you'll always need to enter a password, when plugging it in to use it.

8TB or more would be a hub, being it is expected (on the Manufacturer's part) to be used by multiple devices, simultaneously. Here is Seagate's Options: https://www.seagate.com/products/external-hard-drives/one-touch-external-drives/ Go to: Hubs > Click on the capacity on right of the page.

Data Recovery Plans:

A local retailer offers data recovery plans on these drives, and it only goes for about 10 or 15 bucks. If one did not purchase the data recovery plan, one would pay 1,500 bucks, just to get the data extracted from it. It is sent out to a lab to get this drive serviced and its data extracted. So, consider getting a data recovery plan, when purchasing one. Seagate provides the service plan's services --the retailer sells the plans at the register.

Creator_needs_help Said:

"You have been absolutely, positively awesome in your help to me.: I'm extremely grateful. I will look into all of this!!"

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Thank you. Let us know how it ends up working out. Proud to have helped.

I’m unsure as to why the 2TBs should be reformatted. They’re not intended to be TimeMachine backup drives. They’re source drives to be backed up by Time Machine.

That’s my understanding.

I think I understand you’re suggesting that both 2 TB drives should ideally be APFS.

One appears to already be APFS as it has a container.