Failover for business continuity

[Eric Luyten]

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.