WHM Migration

This is not the best method for zero downtime, but since this feature was added not to long a go, I am throwing it out there. The WHM bulk account copy feature has the "Express Transfer" feature which can help speed up account transfers between cPanel based servers.

Copy Multiple Accounts/Packages from Another Server

You can speed things up if you lower the TTLs for every domain name down to 300 seconds the night before on your old server and it will speed up propagation time even more.

 

It is most likely due to the fact that the DNS is cached at your location/ISP. If you lower your TTLs down to 300 seconds, it will speed things up in most cases.

 

The feature doesn't forward traffic. It changes the DNS zone to reflect the new IP address on the new server. The domain still has to go through DNS propagation as a result. To speed up DNS propagation, you can lower the TTLs on the DNS zone to a low value (I use 300 seconds which is 5min). If you are running your own namesevers, you can update the TTLs in the WHM under Main >> DNS Functions >> Edit DNS Zone and then wait ~24hr for the TTL change to kick in. Once you do that and then transfer the site with the Express Transfer feature, you will see DNS propagate much faster to the new IP address and thus a lower amount of "downtime" occurs.

Hope that points you in the right direction.

 

You can eliminate downtime by running both servers during the transfer and updating the DNS zones on the old server with the new server IPs.

However, in regard to what you said about MySQL (and unmentioned email also), you will have some visitors connecting to the old server and some visitors connecting to the new server during the first 24 hours and there is little you can do about that without overhauling your server configuration entirely such as setting up MySQL on a 3rd server or using a MySQL cluster type configuration which can be complicated to setup and can cause the very downtime during setup you are trying to avoid.

The best method is really what I said where you copy everything over to the new server, update the DNS zones on the old server to point to the new server, and then switch the actual DNS servers which will give you the quickest and most seamless transfer.

As far as those few visitors still connecting to the old server during this brief period, your options are either do a final copy and merge and data again from the old server after everything finishes transferring or turn off the original sites so that those still connecting to the old server know that they are connecting to the wrong server.

 

Best method that I know of is this:

If you are hosting the DNS on your machines then setup a cluster between the old and the new. Have them sync changes. And then use the Express Transfer option for each account. Works like a charm. :D

Edit: After all accounts are transferred I disable MySQL, FTP, Cpanel, Apache.

 

How did this work out for you? I am planning to do almost the same with a few days.

I first will have to find out how to host my own DNS... did that back in 2004 but can't find that tut.

 

Thank you!

 

Pardon me for bringing this threat to life again.

In order for this to work, I need to change only TTL for A records on all the accounts on server, right?

I'm used to having my servers managed and have little experience with this.

Detailed info on this subject would be greatly appreciated.

 

The TTL tells ISP's and your computer how long to cache that value for, You can set it to something extremely low, like 30 or even 5 to make sure that as soon as you make the change of IP address people will be updated instead of taking a few hours as is default most of the time.

You will need to change the TTL for all sites that you're going to change the IP address of. Once you change it to very low you will need to again wait a few hours until your ttl change will take effect. At that point once you change the IP on your sites they should all start pointing to the new server within a few minutes or seconds depending on your TTL.

PS, after everything has been changed to the new server and is working great make sure to put your TTL values back up to something higher like 3600.

 

Thanks, but your comment did not answer my question:

In order for this to work, I need to change only TTL for A records on all the accounts on server, right?

I see that my A records have a TTL of 15 minutes now, but my DNSs have 24 hours.

Should I change these too for all accounts?