BIG-IP slow under ApacheBench

Hi,

 

We are experiencing very mixed performance using F5 BIG-IP. We have done some testing based on ApacheBench and the results are as follows:

 

PNG image, 1,6KB

 

ab -kc 100 -n 5000 http://site.com/image.png

 

Requests per second: 301.05 [/sec] (mean)

 

HTML file, 0,3KB

 

ab -kc 100 -n 5000 -H "Accept-Encoding: gzip,deflate" http://site.com/index.html

 

Requests per second: 934.81 [/sec] (mean)

 

We have expected 10-20x better results, it looks like there is something wrong here. We have eliminated all possible issues, but this is the best we could get.

 

• made sure that the files are really cached by BIG-AP AAM (stopped origin server, the files stayed accessible)
• checked every possible settings page to remove any limits or throttling
• checked interface speed, it is 10G (10000 at Network - Interfaces)
• increased nat instance size from micro to xlarge, zero point zero improvement
• checked license (Evaluation), it doesn't seem to place any limits
• used multiple load generation servers, minor improvement
• ran the test against https://site.com/tmui/login.jsp (different interface), results weren't better
• interesting fact: throughput didn't get beyond 10Mbs according to the F5 Dashboard

We are using BIG-IP 11.4.0 Build 2384.0 Final. Our AWS configuration is based on http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ve-ec2-setup-11-3-0/2.html. I can send you our F5 configuration file, if needed.

 

What can cause this?

 

Thanks you!