Since fixing my Hanging at Verifying DMI Pool Data issue, I've noticed that if I hibernate my PC instead of shutting down, it takes around 20+ minutes for it to restart. The circle of dots moves very, very slowly.

While starting from hibernate, if I press the reset button, the computer starts quickly - the dots spin and the usual speed.

So, anyone any idea what is going on with Hibernate? Why does it take so long to start up and what is happening in the background while the circle of dots are very, very slowly spinning?