will rand() cause performance issue

I still do not understand why you cannot use single pool with "Load Balancing Method" set to "Ratio (Member)" and then setting the vip to use "Default Persistence Profile" "cookie"...

 

 

Regardless, I don't think you are going to beat rand() for way you are trying to use it.

 

 

To note, your times really didn't jump up that much in the example times you provided. Your average time without rand was 350114 and your average time with rand was 466582. It is worth noting, your sample sizes for the comparisons were quite different - potentially skewing these statistics While you sampled 3561 requests with rand, you only sampled 16 times without rand.