Extend Time Machine storage with a second usb drive

[borgusio]

Hello,
I own ca. 5 TB of documents. 2 TB are media and 3 TB is other stuff

I own a 4TB WD Element which is my time machine that I have used for the 3 TB of other stuff so far. I have excluded the media folder from time machine
Then I have always done manual backup of my 2TB of media on another external drive.

I have now purchased a second 4TB WD element usb drive and added this to time machine configuration. I then removed my media folder to those to be ignored. It did backup an additional 2 TB, which added to the other 3TB was a total of roughly 5TB, as it should be.

However, today the first time machine disk shows an error saying that backup cannot be completed because 1,83TB of space are needed (exactly the same amount which is on the second drive) and only 200 GB are available (because the 3TB have an history of course).


What I did wrong and how do I fix this?

I just want to have the two 4TB drives to be used to backup the full 5TB system (for me also ok if one drive does the media and the other one the system, but I would like too not have to do it manually, but rather through time machine).

Thank you all

 

[BrianBaughn]

I'm pretty sure that TM can't split a backup between two drives. Users with two TM drives are using them as duplicates…rotating them and perhaps storing one offsite.

I don't know if changing TM exclusions in "Options", depending on which drive is being used, would work…but that's not "automatic"

I use Carbon Copy Cloner to automatically backup external drives to other external drives (as well as clone my Mojave system drive).

But I could be wrong!

 

[borgusio]

Thanks brian, exclusions work well but cannot be selected per drive unfortunately. On Carbon copy cloner do you do it manually or there is a way to automatise it?

 

[BrianBaughn]

Thanks brian, exclusions work well but cannot be selected per drive unfortunately. On Carbon copy cloner do you do it manually or there is a way to automatise it?

It's either way. My CCC auto-backups occur while I sleep. The manual ones are manual because I don't leave the backup drives connected.

 

[Fishrrman]

Try CCC (or SuperDuper).

You won't understand how well CCC works until you try it.
It's FREE to download and use for 30 days:
Carbon Copy Cloner - Download

If for some reason it doesn't meet your needs, just erase the backup and start over with something else...