8 minutes for 50MB sounds like a lot. Are these zip files?
Depending on whether you are using Tags or Content Categories and other configuration items in the policy, there may be scope for improvement.
In order to scan files, depending on the system hardware the application is going to take some time.
It eventually comes down to this: Security vs. Usability. If you want to be more secure, be prepared for some delays / performance impact (just like with any other security product, e.g. antivirus).
As long as there is good Governance in place i.e. backing from the Management Team on the data protection initiatives (the way it is supposed to be) and security awareness training, users would eventually understand why companies need to protect their data (and how that affects performance).
The files were a proprietary image files (not common image files like jpg, tiff, etc). We are using content categories for that as well. I do understand this is as designed and is more secure...I do get it and do agree. However due to the nature of our business, we have many staff that copy data to/from USB and/or manipulate data on USB devices often. So our intent is to be as transparent as possible and mainly to allow our staff to keep doing their jobs. So I was wondering how others manage this or if everyone just enables it and forces their users to accept it. Thanks again for everyone's comments and suggestions!