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Web server failover using dns

Posted on 2010-09-10
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Last Modified: 2012-05-10
I currently have two web servers. Each located on different ISP.
Seeing how DNS round robin only provides load balancing and not redundancy,
I wanted to go with another option. I found this article from ‘wight-hat.com ‘that suggested
to put the put the DNS service on each web server.  And modify the name servers on the
original DNS server. Name Server 1 will point to Web server 1 and Name Server 2 will point
 to Web Server 2. In this Case if the DNS is unable to reach it’s Name Server 1
“Also the Web Server 1” then it will try to contact the Name Server 2 “Also Web Server 2”.
 All hosts (A records)  will supply the correct IP address to contact the available web server.
 Is this a viable option?
What are the pro and cons to doing this?

 The article can be found here
http://www.wight-hat.com/guides/hosting6.html
PS Web server runs on Windows 2003 IIS 7.0
Thanks in advance
Keith

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Question by:kwolbert_IT
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by:rfc1180
ID: 33648117
>http://www.wight-hat.com/guides/hosting6.html

DNS Global Load Balancing is a great method; however, the method they use: http://www.wight-hat.com/guides/hosting6.html

I would not recommend(I would not use their method in my environment!); you need a solution that contains healthchecks for the servers; if you want a reliable, efficient and scalable load balanced environment, then you need s system specifically designed for that. The method they use still imposes delay due to the necessary re-query.

Some Vendors that offer DNS Global load balancing:

http://www.f5.com/products/big-ip/product-modules/global-traffic-manager.html
http://www.brocade.com/forms/getFile?p=documents/data_sheets/product_data_sheets/serverIronADX_DS_05.pdf
http://www.radware.com/Resources/dns_load_balancing.aspx

Billy
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by:kwolbert_IT
ID: 33648395
Thanks for the reply
But I am not really concerned with the load and the scalability.
Just the available of the servers.
This is really just a Hot Site.
Thanks
Keith
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Expert Comment

by:rfc1180
ID: 33648771
Well, I still stand by my solution; I would not offer any other solution besides a dedicated device that is designed for load balancing. Basically what they are doing is by passing what a dedicated load balancer is designed to do and also lowering the cost. You should always consider scalability in our design, I just would not have it any other way.

Good luck to you

Billy
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Author Comment

by:kwolbert_IT
ID: 33649013
But no load balance is required in this design for this is a Hot site, which sould only be used when the other is not available and adding a load balancing device is another point of failure

As always
Thanks for the reply
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Accepted Solution

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rfc1180 earned 125 total points
ID: 33649147
I think you are missing the point what a load balancer does and what it offers; yes, there are algorithms that offer metrics for "Load" balancing, but typically are used for failover in the event that one if one Web server fails, the others in the cluster will continue to operate or you can setup a backup server in the case that if the primary fails, the backup resumes control. There is only a single point of failure if you design the load balanced environment as a single point of failure.
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Author Closing Comment

by:kwolbert_IT
ID: 33795438
Only wanted to do it his way didnt want to try to help me in the way I asked
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Expert Comment

by:rfc1180
ID: 33795669
>Only wanted to do it his way didnt want to try to help me in the way I asked
Funny, you did ask: "What are the pro and cons to doing this?"
I gave you the pros and cons:

"efficient and scalable load balanced environment, then you need s system specifically designed for that. The method they use still imposes delay due to the necessary re-query."

Billy
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Author Comment

by:kwolbert_IT
ID: 33798660
You right about the way I worded the question. How I should have asked was “Would this work”.
I understand what you described and how it would work. The problem that there is no more budget for this project. I appreciate you taking the time you try to help me on this subject.
Thanks
Keith
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