by Ken Task.
Uhhh ... nope! Not what you asked ...
"Let me check it with you (and other colleagues). Is it true that on non-Window, non-ISS server platform, it is possible to make Moodle back up bigger than 2GB? In other words, I want to make sure that the problem is in ISS."
So was verifying that indeed backups larger than 2 Gigs could be made on Linux platforms - 64bit systems.
Thought @Matteo Scaramuccia determined that it is a Windows/PHP issue ... 32bit. Follow the link he provided.
'spirit of sharing', Ken