[CentOS] High Availability using 2 sites

Benjamin Smith lists at benjamindsmith.com
Fri Jan 6 02:42:51 UTC 2006


On Thursday 05 January 2006 13:15, John Hinton wrote:
> It is important to use TTLs for the various services within a specified 
> range. Too short will get you ignored, at least after a while. Too 
> long.. same thing. I've never had a problem with setting the TTLs low 
> for a few days before a transfer or some such, but then set them back up 
> into acceptable ranges after the move.
> 
> Good help on the proper ranges can be found on http://dnsreport.com

Tried that. Suggestions?
http://dnsreport.com/tools/dnsreport.ch?domain=schoolpathways.com

> Five minutes will more than likely get you ignored after a few days or 
> weeks. Imagine if everyone set their TTL to five minutes.. the root 
> nameservers would be looking up every record on the net once every five 
> minutes... a pretty arduous task for 13 servers. And if you want to find 
> out what happens if you don't use cached DNS, try turning it off at the 
> router level sometime for fun.... s--------l----------o----------w!!!! 
> Heck, 1200bps dialups act like T-1s compared to no caching.

That's fine - but how do I minimize downtime in a failover scenario? (Thus, my 
questions about BGP, which you don't seem to mention) 

In the past, when I 'cut down' the TTL to 5 minutes, I did so about 1 week 
before the switch. (that was the TTL on the domains, so it was the shortest I 
could do it.) I still had the aforementioned problem. 

-Ben 
-- 
"The best way to predict the future is to invent it."
- XEROX PARC slogan, circa 1978



More information about the CentOS mailing list