I think if you have a power outage and both the DVR and external HD turn
off at the same time you may not lose your data. If the external HD is
disconnected from power but the DVR still has power, the DVR will look for
the external HD but not find it and then revert to the internal HD and then
require you to format the external HD before it will work again.
On Sun, Nov 23, 2014 at 8:57 PM, shannon01 <directv-admin@forums.directv.com