Ram wrote the following on 5/30/2012 8:53 AM: > > 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 use a VPN to easily move the IP address from one location to another. This could be accomplished in several ways: a site-to-site L2 VPN allowing the use of a single subnet at both locations; an imap server to router VPN allowing whichever server has an active VPN connection to assume the "active" IP; I'm sure there are others. I would think a VPN would be simpler and thus more reliable than using a front end proxy. --Blake ---- 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
