I have created an installation USB (Sandisk Cruzer, USB 2.0) and its performance is fairly good - firefox and all other applications run pretty smoothly. I wanted a portable setup, so I installed Ubuntu 16.04 on a PNY 64 GB USB 3.0 drive. I have an 500mb Fat32 partition for EFI, an 11 GB swap partition, and the rest as an ext4 partition.
I had some initial booting problems (graphics) which seems to be miraculously resolved by some restarts. However, performance is extremely slow. By that I mean that the Live Ubuntu of the Sandisk USB 2.0 drive loads is ~10 seconds, while the full installation from the PNY USB 3.0 pendrive loads at ~10 minutes. And it is extremely laggy.
Any idea what should I do?