MPX for one folder in linux

Hi,

I have big data size 5TB in one folder, for example : /data/big
It containts many files and sub-folder.
I enabled cross mount point and 5 mpx, but look likes its only generate 2 JobId, consider as 1 mpx.
How to enable 5 mpx, so its generate 5 JobId in different drive?
(Objective, I want to backup 5TB in one folder in less than 8 hours)

How I can see, some JobIds for some clients write data to drive?
IE: id 1291, 1292, 1293, from client1, client1 and client2 write to drive 1
So, I can know 1 drive handle 3 jobs at the same time.

Thanks,
Santave