I have an external 1TB USB 3.0 drive. I would like to keep some sensitive files on it, that would like to have encrypted, but I don't necessarily need the whole drive to be encrypted. In fact, I would rather have part of the drive unencrypted so that I can plug the drive into a colleague's Mac to access files we are collaborating on, without allowing access to the encrypted files. I know that I can create an encrypted disk image on the drive, and keep all of the sensitive files in said image, while leaving the rest of the drive unencrypted. My question, however, is whether I can expect any performance hit accessing the files off of the encrypted image vs. simply formatting the drive with encryption from the get-go and just having the whole drive be encrypted. In other words, will access to files on an encrypted disk image be any slower than access to the same files on a fully encrypted disk?