On 05/30/12 19:23 +0530, Ram wrote: > > >On 05/30/2012 02:26 PM, Eric Luyten wrote: >> On Wed, May 30, 2012 9:24 am, Ram wrote: >>> On 05/30/2012 12:43 PM, Dmitry Banschikov wrote: >>> >>>> On 05/30/2012 10:52 AM, Ram wrote: >>>> >>>>> I am trying to setup a remote cyrus-replica to a different geographical >>>>> location for business continuity. >>>>> >>>>> In case the main server goes down the users will get switched to the >>>>> remote server by making a DNS change. The only issue is DNS replication >>>>> would take a long time so the switch is not instantaneous. How would one >>>>> make the switch instantaneous ? Moving the IP is not possible because the >>>>> Remote server is on a different network >>>>> >>>>> >>>> You can set TTL of RR to very small value (say 60 seconds). In this >>>> case, DNS change will be propagated fast. >>>> >>>> >>> But I have seen some DNS clients , especially on windows , do not honor >>> TTL. >>> For a 10 minute TTL , even after 4 hours the windows server keeps >>> resolving to the old server >> >> Ram, >> >> >> Correct. >> Some OSes/applications/resolver libraries will keep on using the 'old' >> values until *they* see fit. >> >> DNS-based failover is (and always has been) a very low cost, halfbaked >> solution. Been there, done that... >> >> >> Eric. >So if not DNS based fail over , what is the other alternative. >I cant move the IP , or re-announce BGP >I cant have both servers in active-active mode You could configure Cyrus frontends (proxies) located at both locations. If there is a backend failure, then you wouldn't need to depend on DNS propagation for restoration of service. That would gain you a higher level of availability in the case where your network, and your frontends, have greater stability than your backends. You could also implement BGP anycasting for your DNS servers and/or your frontends, which is how I understand the content distribution networks implement failover. -- Dan White ---- Cyrus Home Page: http://www.cyrusimap.org/ List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/ To Unsubscribe: https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
