Amount of files getting decreased during upload

Hi,

we had a RHEL 6.1 system from where we were uploading very good amount of files to another server.( around 8000 files/min) without any issue.
But when we upgraded the same system to RHEL 6.4 and later 6.6 we faced a issue. That number of files being decreased and became stabled around 3500-4000 files/min.
When we restart the uploading again its starting with full load but later its coming down.

Not able to understand what is the issue. Our Upload server remains same always.

any pointer ?