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Simon_Wright_85's avatar
Simon_Wright_85
Icon for Nimbostratus rankNimbostratus
Oct 31, 2008

Pool statistics question

Hi

 

 

I am seeing some figures in the pool statistics screen that are confusing me and wondered if anyone could clarify what it is that I am seeing.

 

 

We have a pool of two servers that is setup to use the Round Robin loadbalancing method. When I am viewing the statistics screen for the pool i am seeing the total number of connections to each of the members increasing at the same rate.

 

 

The requests column is the bit that I do not really understant though. After a bit of time each member had reached 12 total connections but had very different numbers in the Requests column.

 

 

When using the Round Robin loadbalancing method does this just loadbalance the connections in a uniform way or should it also do the same for the requests? The other strange thing is that even though the members had 12 connections each the requests were six for one server and 65 for the other. Any ideas why one server had less requests than connections?

 

 

We are using LTM 1500s running 9.4.4 if that helps

 

 

Many thanks in advance

 

 

Simon
management
monitoring
  • dennypayne's avatar
    dennypayne
    Icon for Employee rankEmployee
    Nov 04, 2008
    The initial load balancing decision in Round Robin mode should be uniform, but several factors can influence whether the traffic continues to appear uniform in the stats, the primary one being persistence. If you are using source IP persistence on the virtual server that uses this pool, any clients that come from behind a NAT or proxy will appear as a single client to LTM and will be persisted to the same server. This could lead to a disparity in the number of connections to each pool member. Cookie persistence can alleviate this somewhat.

     

     

    Secondly, if OneConnect is enabled then LTM attempts to re-use server side connections so as to reduce TCP overhead between LTM and the servers. So multiple connections on the front side end up as one connection on the back end.

     

     

    Thirdly, it could just be random traffic patterns, if the users on one server happen to access more content than users on the other server, their request count could end up higher just as random chance.

     

     

    Denny
  • Kevin_48708's avatar
    Kevin_48708
    Icon for Nimbostratus rankNimbostratus
    Nov 18, 2008
    Hi

     

     

    I have a follow on question to the one posted by sjw7. What is the difference between Connections and Requests?

     

     

    Cheers

     

     

    Kevin
  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Nov 18, 2008
    Hi Kevin,

     

     

    A connection is a TCP connection. A request should be an HTTP request. The online help in 9.4.5 doesn't list any detail for requests. But you could do a simple test on a VIP by adding an HTTP profile, making a few requests and then checking the requests stats column. It should increment. If you remove the HTTP profile and then retest, the request stats should not increment.

     

     

    Aaron