Q: Continuing to use Time Machine after re-installing OS X

Hi,

So I just formatted my hard drive and re-installed El Capitan. I didn't restore from my time machine back up because I wanted a super clean refresh. I backed up my own files and put them back on my hard drive when i was done.

Ok, so now everything is all fresh and running all super snappy. Great.

Question - if I turn Time Machine back on will it simply continue to back up? Or will it be confused about how theres apparently a new computer there now?

Or will it simply back up the new stuff but keep the old stuff on there? Which would be a total waste of space...

Or do I have to format the Time Machine drive too and start backing up all over again?

Please let me know if you have any ideas on this. Thank you!

Andy

Message was edited by: andyg74 Edited for clarity