updating to iOS 5 issues

Hi! I'm not sure if this is the right spot, but I need some help with updating my iphone to iOS 5. I currently own a 32GB iPhone 4. (bought in july. I have the best timing) I'm still using iOS 4 but would like to update to iOS 5. Since there is not enough space for all of my music to be stored on my macmini, it is currently stored on an external harddrive. Is there any way I can get my iPhone to back up to that harddrive and then restore itself from there when I do the update? Thanks in advance!

I'm confused. Your phone has to be synced with your computer, ergo the music must all be backed up on that computer (or an attached HD). Your iTunes will store its music on whatever drive you tell it to, and that's also where it stores its backup and sync data of your iPhone.

IOW, I think this is a non-issue.