The goal is to periodically conduct a test restore from Time Machine to external usb drive. Main point is that for duration of the restore the Mac must not be blocked just for this operation only but to let the restore run in background while being able to do regular work in foreground. Basically it should not be a big problem cause the TM data is on network and restore destination is the external usb drive. OS X is started from internal HD. Till now I found one single way to do recovery from TM: recovery mode by booting with cmd+R. However it does not meet the requirement of concurrent restore with regular job. Any chance to achieve the goal?