Encrypting Entire Hard drives

[Richard B. Tilley]

If this is in the faq, please forgive me.

How well does GNUpg encrypt entire hdds or whole partitions? 

I have lots of senetive material spread out over several partitions and 
several drives. I think it would be easiest and fastest if I could just 
encrypt all the hard drives instead of trying to encrypt the indiviudal files 
and directories. Has anyone here had experience doing this?

Thank you,
-- 
Richard B. Tilley