ACE 4700 hash address source

Unanswered Question
Dec 22nd, 2009

Hello I'm using an ACE4700 to redirect connection toward 2 Cache boxes (cache2 and cache3).

I'm using "predictor hash address source".

On the cache boxes I see that on the first one I have 400 src IP and on the second one i have 200 src IP.

I was expecting to have half ip src on one cache and half on other one.

Since the predictor is based on "hash address source" the two cache should be loaded with the same number of ip src.

How can I view on the ACE the src IPs redirected to cache1 and the src IPs redirected to chache2 ?

serverfarm host proxiesAC
  description Batteria dei BlueCoat
  failaction purge
  predictor hash address source
  rserver cache1
    probe probe_ICMP
  rserver cache2
    probe probe_ICMP
  rserver cache3
    probe probe_ICMP
  rserver cache4
    probe probe_ICMP
  rserver cache5
    probe probe_ICMP
  rserver cache6
    probe probe_ICMP

I have this problem too.
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Gilles Dufour Wed, 12/23/2009 - 02:10

When described like this, it sounds easy to find a hash algorithm which will split 600 ip addresses in 2 equal size groups.

But this is actually very complicated.

First because when we designed the ACE code, we didn't know how many ip, which ip ... would be used.

Morever, this information changes with every customer of ours.

In conclusion we made a generic algorithm which works most of the time.

But this algorithm can't guarantee that you will have equal loadbalancing.

If you need equal load on your caches, you need to switch to leastconn or roundrobin.

Finally, I don't see the need to use hash address source.

Usually when using ACE with caches, we use either hash url (if we want to make sure one object only exists on one cache - save disk space) or roundrobin/leastconn to have equal load on the caches.




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