[aterz]

Hi everybody
I've raspberry Pi with rasbian and xbmc. I connected a 3tb samsung hd to the raspberry. File system is ntfs (the one originally formatted).the hd has external power supply and it is directly connected to usbo of the raspberry with no hubs in the middle.
The hd is authomatically perfectly recognized and mounted. The cable is perfectly inserted into the usb port.
My problem is that every now and then the raspberry unmounts the hd and mounts it again after 10-15 secs.
This fact makes the video Im looking at stop and even the other services like samba has problems of course.
I noticed that it is more likley to unmount and mount again in the moments in which Im asking more effort from the hd in terms of data exchange. Does anybody has an idea of any possible solution? Many thanks
Andrea

[mayoman]

I know you have an external power supply for the HDD, but it still sounds like a classic power supply issue. (HDD unmounts when voltage drops below 4.75V and remounts when it rises again).
It may be the Pi power supply itself that is at fault - worth trying another power upply if you have one. Have you the ability to meter the Pi voltage? It would be worth it to rule out voltage drops as an issue.