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manc_63343's avatar
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May 04, 2011

How do other co's use Global Load Balancing with multiple DC?

How do companies like google, yahoo use global load balancing accross multiple data centers? When I do nslookup I see they are doing DNS round robin within each data center.





Non-authoritative answer:








3 Replies

  • Hi Manc,



    Some major services do use a single IP. You can check netcraft for some examples that are using GTM with a single IP response per A query. When clients to get multiple IPs in the same datacenter, it could be multiple virtual servers that all do a hash based load balancing/persistence to get clients back to the same app instance. Or they could have shared memory/database for session information and not need to persist sessions to the same application instance. There are quite a few options in this area.



    Here's an interesting discussion on ServerFault with a few relevant points:




    Are you trying to address something specific in your situation?



  • I am trying to find out gmail, or yahoo email do load balancing and how they failover. I got some information on the net but not clear how they really use it.



    for eg: I posted nslookup and it doesn't show any WIP that would indicate they are really using GTM. It looked like DNS round robin.
  • Well, netcraft shows google doesn't use BIG-IP, so I'm not sure how they handle intra-DC sessions. But I would imagine they either have persistence or hashing from the front end web servers to the app server which holds the session information or their app servers are able to access a shared memory store with the session data.