Looking for ideas regarding Server/DNS migration

[jfall]

I have 7 cPanel servers that I'm migrating to 7 new cPanel servers at a different data center. Since I am moving to a new data center, I am unable to keep my IP's. Migrating the accounts etc isn't going to be a problem, however I am looking for ideas on how to best handle DNS.

Each of the 7 servers are currently running their own set of name servers, there is no clustering involved. I am thinking that I could use the same name server hostnames on the new servers than just switch the IPs at the registrar when the accounts are copied over. This would prevent users from having to update their name servers. The only problem I see with this is that propagation will cause data to be at least 24 hours old which may be a problem.

What is the best method to go about this? Is there a better way that I can migrate the servers without causing a problem with outdated files due to propagation?

Thanks in advance!

[chirpy]

You've pretty much talked your way through it There's little you can do to avoid the 24 hours propagation timeframe. You van reduce the zone file min TTL, but that doesn't usually help that much since many ISP's ignore anything less than 24 hours.

One thing that you can do, if you have any important MySQL databases, is to migrate everything across and then make th switch, then on the old server modify the scripts that access the MySQL databases to use the IP address for te new server (an make appropriate changes to the MySQL access privileges).

Long and short, if you're changing IP addresses (and you're with a different datacenter so they cannot temporarily reroute the old IP addresses to the new ones) there will always be a window when visitors can be going to both servers.

[pshepperd]

I have moved a couple dedicated servers, what I usually do is just that, reduce the TTL, this seems to work quite well for me as I have not yet had complaints. I usually set it down to 20 minutes which does cause extreemly high server load for 24 hours, after resetting the TTL I wait for 24 hours, for all the cached zone records to expire, and then move all the sites.

Dunno, seemed to work for me, resetting the TTL I think has varying success, mostly due to how your dns is setup, I think a lot of times ISPs will rewrite the TTL on certain types of records, like cname and alaises but not MX and A records (to a certain extent).

Also, If you can I would set up one master name server, possibly with very few sites on it (minimize downtime), but all the other ones are slave to it and when dns changes occur, they are set to notify each other.

My registrar seems to update the root servers almost immediatly, so as long as your TTL's are set low, I think it will work ok, I would notify all my clients that there is going to be "something" happening though, a notified client is much more receptive to turbulance

Good luck.