I'm going to be moving a site to a new server. It's an E-Retail site running on Linux with a Plesk control panel. I'm trying to devise a strategy to make the transition with the least downtime and the ability to revert back to the old server at the drop of a hat.
First off, I'm thinking it is best to configure the website with the same URL as the existing site instead of creating some variation like putting 'beta' at the beginning of the URL. This way I won't have any unexpected suprises if I change the site name during transition.
So the only way I can get that to work and still have the existing site operate would be to test from a workstation that I have configured to use the DNS on the new server so I can use the existing URL to test the new server, while everyone else on the Internet still goes to the old server.
Then leaves the issue of IP address changes when it comes time to actually swap servers. Would it be better to simply cut the TTL time down on the production DNS to like 15 minutes, then simply change the IP address for the domain, OR, would it be better to simply unplug the network cable on the old server, then change the IP address on the new server to the old server's address. If something goes wrong all I have to do it unplug the new server and plug the old server back into the network. It seems this also would be the 'safer' method from the aspect of some not having the chance that some clients may take hours or even days to get the IP address update due to improperly configured proxy servers, etc.
I would just unplug the old server and switch the IP's to the new one. Its quick and easy, might take 5 minutes at most. You could even just copy your whole harddrive over as is, or switch physical harddrives.
That won't work (copying the hard drive) as one of the main reasons were are changing servers is to switch to more recent versions of all the software (O/S, Plesk, Apache, PHP, Perl, etc.)
Switching IP addresses on the servers is also going to be touchy as various configuration files all over the server are going to have references to the IP Address the server (and website) was initially setup with. I'd have to go change it everywhere. Plus I can't test the new site using the same IP address as the existing site.
It's looking more like changing the address on the DNS may be the way to go?