Pretty minimal. If you have TrueCrypt installed you can run a benchmarks of various algorithms. It's especially fast if you have a modern processor with AES-NI

Pretty minimal. If you have TrueCrypt installed you can run a benchmarks of various algorithms. It's especially fast if you have a modern processor with AES-NI (hardware AES instructions) -- I get around 1GB/s Encrypt/Decrypt using AES on a Core i5.