If I copy a time machine backup (on external hard disc) to another external hard drive and then keep that backup updated with rsync, will that give me a valid backup of my time machine backup drive? With valid I mean that I can use that backup of the backup to restore my data just like with the "original" time machine backup. Or is it possible to have 2 time machine backups in parallel (e.g. one always plugged in for an hourly backup and the other one plugged in once every (other) day) for some additional backup? Or what's the best way to keep a second backup?