I was searching for documentation about the HP Lefthand P4500 series when using Flow Control on the switch ports but i didn’t find sufficient information to make decision. We decided to test it ourselves.
The HP Documentation says you need to enable flow control on all ports connected to the P4500, you can read this in the best practice, but on the forum you can read about users that deactivated it after having performance issues. While i was reading i noticed that these users were also using Jumbo Frames on that exact same ports.
As i wrote in my post about Jumbo Frames: “Jumbo frames are commonly used with networks that carry large amounts of data (or big files) or for purposes like iScsi.”
When you enable Jumbo Frames on the switch together with flow control this causes an enormous load for the switch, explaining the performance issues of most users. So you have to make a decision; or enable flow control without Jumbo Frames or use Jumbo Frames and forget about flow control.
We have tested this with the HP P4500 (2x) trunked with LACP on a Procurve 2810-48G switch. Our performance with only Jumbo Frames enabled is outstanding!