I have problem when try to open big file (file with size 6Gb or more) in hex mode with hex editor in linux (I use okteta, hex editor, etc). Because this program will read file in memory so program will freeze when try to load this file. But my problem solve when I use bless as hex editor.
Bless editor have features to editing of large data files and block devices. You can check about features from this software at website http://home.gna.org/bless/. From my opinion, this software is my best linux hex editor.