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DNS Loadbalancing across AD Sites RRS feed

  • Question

  • I wish there was a way where I have users (or applications) trying to access http://website1/

    So there computer queries DNS to get the IP for website1.  Then DNS determines which of two ips to give the person based on where the person is requesting the ip from.  If they are in site1, they get IP1, if they are in site2, they get IP 2.  This would mean that you could have local web fronts or back end sql servers that are local to each site (ie low ping times), but can in the back end replicate there data to each other by using the ip address of the others.  This allows quick easy load balancing (the same web application is split between diffrent computers), and disaster recovery (all you do is change DNS to point to the one that is still up), and provides quick access (ping times to go across the country or world can be 200+).  Micrsofts clustering service and load balancing doesnt seem to work, as clustering is a just a fail over if one computer goes down (provides no cross site/subnet support) and no load balancing, while the load balancing service means that each server must be on the same subnet and doesnt allow me to speficy that I want one server to accept all incoming connections to SiteA (because the server is near siteA) and another to accept all locations from siteB (because its closer to that).

    Friday, March 2, 2007 9:05 PM

All replies

  •  

    I wish this would work as well!

    I guess there would be problems with DNS translation caching, possible DNS server problems and so on. A related question:

    Has anyone done a similar thing with a webserver? Could you access a web site which then redirects you to a host that will handle all your subsequent requests? The redirection could be handled by a script that decides where to redirect you to. For example, source address or current server loading could be used in the scripts algorithm. The webserver itself could be clustered for resilience.

    This would avoid the need for an external Web load balancer and also prevent all traffic from being funnelled through a single device.

    If you want a simple load balancer appliance have a look at loadbalancer.org.

     

    Monday, March 5, 2007 6:05 PM
  • I found this site which gave alot of information on the subject.

    http://tenereillo.com/GSLBPageOfShame.htm

    It says:

    The use of multiple A records is not a trick of the trade, or a feature conceived by load balancing equipment vendors. The DNS protocol was designed with support for multiple A records for this very reason. Applications such as browsers and proxies and mail servers make use of that part of the DNS protocol.

    and

    The only way to achieve high-availability GSLB for browser based clients is to include the use of multiple A records

    However I have no idea how to set up the microsoft DNS to return multiple A records, ordered by ones in closest to the person requesting.  Only way I know of is doing a round robin DNS, which makes everyone connect to a server far away from them most of the time.

    Tuesday, March 6, 2007 1:33 PM