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Scott_Hopkins's avatar
Scott_Hopkins
Icon for Nimbostratus rankNimbostratus
Oct 06, 2010

Connection Mirroring Overhead

I'm looking in to enabling Connection Mirroring on our LTM HA pairs. Does anyone out there have any feedback, suggestions, or gotchas on doing this? I know we'll take a hit on CPU, which we have room to support, but has anyone run into any other problems with Connection Mirroring? The last time we used it was on v4 with 5100's and we eventually had to disable it due to load.

 

 

Thanks in advance.

 

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  • Chris_Miller's avatar
    Chris_Miller
    Icon for Altostratus rankAltostratus
    Oct 06, 2010
    I've never used it and don't know many who do. It really depends on your volume and traffic type. If you're delivering something like HTTP which can handle failover pretty gracefully, there's not much gain.

     

     

  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Oct 07, 2010
    I think the overhead is high enough that you'd only want to use it on protocol-specific virtual servers where the protocol doesn't gracefully handle drops and the connections are long-lived. As Chris said, HTTP/S is definitely not something worthwhile to use connection mirroring for.

     

     

    Aaron
  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    Oct 10, 2010
    I use connection mirroring extensively. Both on long lived connections and shorter lived connections like HTTPS (I guess I'm disagreeing here with a few other people). There are good reasons you don't want even HTTP to break. e.g. on an ecommerce site (When a customers webpage fails, you'd be amazed how many people give up and goto the opposition. Believe me some business managers count transactions that start and fail to complete as a pretty big failure against you).

     

     

    As far as overheads... It's pretty minimal on every site I've done. And IMO the benefits far outweigh the costs... I've had 6400's running with 2000 HTTP queries per second and over 120Mbps of outbound traffic with mirroring and no issues due to load. The few times I have had cause to drop mirroring (To see whether we had headroom for anticipated traffic increases), disabling the mirroring didn't make a big difference in CPU consumption on the active unit.

     

     

    What I could recommend however is having a dedicated network for the mirroring traffic...

     

     

     

    H