3 Replies Latest reply on Aug 19, 2016 7:05 PM by RichardLetts

    Can I speed up the actual failover process?

    mikegale

      More specifically, can I speed up the time DNS takes to update it's records so that the failover is less visible.

      I'm looking to see if there are any switches one can use with nfcmd.exe when FoE goes through it's failover routine and performs the "Hiding" part. I believe at that time it runs a command "DNSUpdate -auto". DNSUpdate comes with several different switches. Has anyone tried to use some of these switches to force dns to update quicker? If that's even possible...

       

      Any help is greatly appreciated

       

      Mike

        • Re: Can I speed up the actual failover process?
          aLTeReGo

          FoE updates the DNS entry almost immediately. What you are likely encountering is DNS caching on your local machine. You can test this yourself by performing a failover and then running the 'ipconfig /flushdns' on your local workstation. Provided you are using the same DNS server the one which was updated by FoE, the change you see would virtually immediate. If you are using a different DNS server than the one that FoE is updating, then your DNS server is also likely caching.

           

          This is perfectly normal behavior for any DNS server, and essentially any client operating system to cache DNS results. You can however control how long these results are allowed to remain cached by adjusting the TTL for the DNS entry. This would be a value controlled on the authoritative name server for the domain.

            • Re: Can I speed up the actual failover process?
              mikegale

              Maybe our problem is not that FoE doesn't update one of the dns servers quick enough but the fact that dns doesn't replicate between servers quick enough.

              When we fail our main app server over, the website is down from anywhere between 5 to 30 minutes. That's if one connects via the hostname, if I connect to the IP address of the now actice secondary server the webpage works. Would there be something that can be changed in dns so that the new/or altered dns entry replicates out to all the other dns servers immediately?

                • Re: Can I speed up the actual failover process?
                  RichardLetts

                  Yes -- ask your DNS engineers about this.

                   

                  1. Make sure the TTL on the resource records is set to 30 seconds

                  - this should mean that the results of DNS lookup are cached for this long

                   

                  2. Set the REFRESH on the SOA record to ~30 seconds

                  - secondary DNS servers will check with the primary DNS server to see if the zone serial number has changed this frequently.

                  - DNS engineers may not like this

                   

                  In my world our Solarwinds servers are [currently] in their own zone that I control [I'm also one of the DNS engineers (I have too many hats)] with a short keepalive

                   

                  Shortly we're hoping to completely stop using DNS updates and switch to DNS load-balancing where the DNS servers maintain a keepalive to the Solarwinds Servers through the FOE-managed interface and will return the IP address of the server currently working (saves us doing a DNSupdates from FOE, and also gives us geographic redundancy).