Planning on downloading Big Sur on my external hard drive, do I need to erase everything?

[jordysak]

The external hard drive I am using is formatted to HFS+ (Mac OS extended) and has about 300 GB worth of stuff. It is a 1TB hard drive, so I still have about 700 GB left and I am planning on using it to try out Big Sur.

I have a 2017 MacBook Air running High Sierra, from experience I know that newer updates can mess up older machines so I want to make sure everything works seamlessly..

Considering that my external hard drive is not formatted to APFS, but HFS+, do I need to format it again and erase everything in order to proceed with the installation process?

I don't want to erase 300GB for this process, so I don't know if I can or if there is a way around this.

 

[velocityg4]

No
HDD=HFS+
SSD=APFS and the OS will convert it during install if HFS

My only concern would be if it is setup for MBR and not Intel Mac Booting (GUID).

You can also add partitions to the existing drive. Then install the OS to it's own partition. That way you can easily wipe it if you decide it isn't for you or clone it to your internal if you want to keep using it. That is what I'd do.

You could also clone your internal to the partition you create on your external. As a backup. Then upgrade your internal to Big Sur. If it doesn't work out. Then boot off the clone and restore it to your internal. A bit more time consuming if it doesn't work out. But makes life easier if it does.

As always. Make sure you have a backup.