I want to reiterate what has said before. Make sure you do an upgrade on your test site or on a local install. Do this to gain confidence in your process and ability to rollback the changes. And as had been said before, really the best way to do this is on your test site, close your production board, backup and mysqldump, import db into test env, upgrade, TEST, mysqldump, import db into production, import new files into production, go live.
