I need to sort how how to back up two MacBook Air computers in my home automatically at night without user input required. The computers' only connection to my home network is via wireless router which could perhaps use upgrading soon. Is there a practical way to do this on site? What hardware and software needed and best? Is offsite backup a good/better option? My concerns are 1. will the system back up automatically even if the machine is in sleep mode? 2. will the system be fast enough to complete back ups in reasonable time? 3. will the back up be reliable? Last - I do have one windows desktop machine that backs up to an attached external usb drive - I could keep doing that or incorporate all three into one back up system - not sure what is best. Any input much appreciated.