So, since I have to move all my accounts from Reseller A + Reseller B to Server A, I've sort of "devised" a plan to get everything moved with zero downtime. However, before I do this I'm asking the WHT community on whether or not it'll actually work, and any tips they have.

Here's the idea;

I transfer the accounts from the reseller to my server, change the ns2 and ns4 nameserver IP's at my registar. Wait a day or two for them to fully propagate. Set it up on the server. Then change the ns1 and ns3 IP's at my registar and setup those nameservers in the server. Now, will this plan actually work? That's what I'm asking. And, does anyone have any advice?

This idea requires time for the dns to propegate fully throughout the internet. I'd suggest something a bit different, but either will 'work'.

1) Copy the sites over to the server, all at once if possible
2) Duplicate the existing dns zones on your server. Hopefully the older provider has zone transfers enabled, so this should be fairly easy.
3) Move the DNS on your sites over to the dedicated server. Traffic is still directed to the reseller accounts.
4) Drop the TTL on the records on your server to something very low (15 minutes or so?)
5) Modify the dns on your server to point back at your own server

That way, the clients get 'switched' in 15 minutes time, rather than 24-72 hours. You can modify this and copy the sites over after the DNS zones have been created, just before you do the switch - might be a good idea for 'dynamic' sites.

This method is basically what we did to move away from one DC to another. Very painless for the clients.

-David

That's true, I could do something like that. However, it'd require the support for reseller accounts to do a bit of extra work, and I don't know if I'd;
A. Want them doing that since, I'd be leaving them after that month. I'd sort of feel bad for all the extra work I'd be giving them.
or
B. Trust that they would actually do that.

Ive done exactly this plan before (changing the DNS TTL window to a short period of time), and it worked very well. Ive even gone down to 5 minutes for the most dynamic sites - just to make sure things dont burp. (make sure your host can handle it - as thats a lot of dns queries coming your way!)

The only problem Ive found is that some ISPs (mostly from europe) ignore the TTL window in DNS queries entirely. They set the ttl to be good for up to one week, no matter what you set your ttl to be. Ive expierenced some visitors coming to old IPs for up to one week after I switched the DNS. Then they magicially stopped. Drove me crazy for a while until I confirmed with one of my european customers that they have had this problem before, and its something that some ISPs do to drive down outgoing traffic.

Point here is, dont switch off your reseller accounts the day after you make the big jump!

Another thing...

If you have a few busy forums like we had, to ensure no 'lost posts' during this you can setup the sql database to be setup on the new server during the transition phase. That way all queries/inputs get sent to the new database on the new server. Definitely not a good idea with sensitive info, but for a forum it'll work. Performance will drag, depending on how many queries the forum takes up, but on the ones we did it wasn't too bad - it was only for the 15 minutes or so that the move took anyway.

-David