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MahendraRaj_131's avatar
MahendraRaj_131
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Aug 30, 2013

GTM for Active / Active DC with component failure detection

Hi All

 

I am preparing a solution to provide the active / active solution between two Data Center to server a website. I am convinced to use the GTM for site selection for inbound traffic from internet. But the question what I have and not clear myself is, what will happen if one of the component in application layer or DB fails..? Will the GTM can recognize it and do the failover to next DC?

 

Would you please advice me on this..!!

 

Thanks Mahendra

 

application delivery
availability
design
devops
iApps
iControl
iRules

3 Replies

  • David__Pasch's avatar
    David__Pasch
    Icon for Altostratus rankAltostratus
    Aug 30, 2013

    Mehendra, The first question I would have is,... Are you using LTM at the datacenters to load balance all three tiers (web, app, db)? If so, this is very easy. On the GTM, under each site LTM, build a Virtual Server object for each tier. Then, under the web tier Virtual Server object, add the app and DB tier as Virtual Server dependencies. Lastly, build you WIP based on the web tier. This way if any of the three tiers fail, the site will fail. This is very common. Another way would be to just create comprehensive monitors at the LTM that exercises all 3 tiers through the web tier, and then just use the state of the web tier for the site status. For instance, a monitor that logs into the web front and runs a query or executes something against the application causing a DB query and looks for a specific response. Not knowing the details of your application, it is hard to describe this much further. Hopefully, you understand my point. 

     If you do not have LTM at the data centers, you can still do this with monitoring from the GTM. You could run a comprehensive monitor FROM the GTM, against the web tier that exercises all three tiers, as option 2 above, and base site status on that. However, I prefer to do all the monitoring locally, as monitoring a site from a remote GTM brings many other components into the equation (WAN links, routers, switches). Things you may or may not want in the decision making.

 I guess the point being, YES you can do this.

    Good Luck! David Pasch

  • MahendraRaj_131's avatar
    MahendraRaj_131
    Icon for Nimbostratus rankNimbostratus
    Aug 30, 2013

    Hi David

     

    Thanks for your help... Yes, there are LTM in all three layers. as shown below...

     

    GTM ->LTM->Web Farm->LTM->App Farm->DB, Cache Server, Payment Server etc..

     

    Now, my worry is how the GTM would know the DB or Cache or Payment server failure..and do the failover !!!

     

    is there any document or URL which could explain me in detail on this config? If so would you please share it..!!It would be a great help..

     

    Thanks Mahendra

     

  • David__Pasch's avatar
    David__Pasch
    Icon for Altostratus rankAltostratus
    Sep 01, 2013

    http://support.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/gtm-concepts-11-3-0/1.html

     

    The GTM will know about the state of the other VIPs via the standard GTM_LTM iquery communications. You will need all Virtual Server Objects configured under the related LTM Server Objects on the GTM. Then under the Web Virtual server object on the GTM add the other Virtual Server objects as dependencies.

     

    David