TomCat said:
It's not harmful to the HDD; when it loses power the actuator just retracts to a neutral position.
It might be harmful to data, but that is rare. As current drains out (and as the actuator is retracting) it can spew a little bit of write data over adjacent sectors, which can corrupt a file or corrupt a tiny part of the database catalog in an extremely-rare worst-case scenario. Odds against that being problematic are very strong, but not a sure thing. Data it is trying to write is media data (which you have already decided you don't need if you are shutting the system down) or indexing data, which picks up right where it left off at reboot, so not really a problem.
A graceful shutdown lets the DVR decide on a stopping point and stop writing before it reboots. A rude one doesn't let it wait. But the difference is pretty small, and the end result is just about the same, so do a menu reboot if possible just to ever-so-slightly increase those already-lottery-sized odds if you can; RBR or yank the power cord if you can't, and don't look back. It really doesn't matter all that much, but a menu reboot can be done without leaving your Barcalounger.
While this is all true it isn't a certainty. It is not true that sudden power loss it never harmful to a hard drive. The hardware is designed to minimize the probability to the maximum extent possible but depending conditions and what the drive is doing it's nowhere near possible to it's "not harmful to the HDD" 100% of the time.
Over the past 25ish years I've installed hundreds of hard drives (yes, I know that sounds like such a huge exaggeration that it can't possibly be true but it is and mostly due to some rather stupid ideas on a managers part). I can tell you that given the right set or circumstances; temperature, movement, reading/writing, age of drive (this is a big one), etc., it is certainly possible to have hardware failure from sudden power loss...or more to the point, sudden power loss followed by immediate restoration of power.
Even with journaling the data is not immune to corruption. And, this is probably more likely that harming the drive.
In the end the percentages are small but certainly not insignificant. I realize you're saying it's easier but only marginally safer to do menu restarts but I feel you have down played the potential hazards. In my experience, do it often enough and sooner or later it will catch up with you.
Additionally, assuming there's five million DVRs, assume a life of four years, assume high MTBF you can expect that
thousands of drives, won't last the four years. For this reason alone I would never potentially hasten the demise of a drive with an RBR.
IMHO, an RBR is enough of a
potential hazard that I recommend it only be done when there's no other choice. To be clear, I do this so rarely that when I'm forced to I'm not very concerned about it. It just don't think it should be a matter of course.
My 2¢ FWIW.
Mike