also run cat /dev/sda, sometimes you may need to trigger a read
Discussion
gonna do that on my devices... even though i do use them fairly often... one of them has an overheating problem, and all of them, even though they have a very decent thermal contact to a decent aluminium heatsink-case, slow down a lot after writing for more than about 5 minutes
also, better to do this:
sudo cat /dev/sda > /dev/null