artie,
I have downloaded ventura onto my HD and after checking it out, I think I will keep it. Question: There are 499 gb on my external HD and 486 gb on my HD. Is that ok to use my external as a back-up?
The appropriate size of a backup disk is dependent upon the amount of data you want to store on it.
Even if you intend to use the external for Time Machine, the standard 3x the size of the internal may be hugely excessive if you haven't got much data on your internal.
