How to Migrate a Web Server Seamlessly with Zero Downtime

by Michael Cropper | Mar 24, 2015 | Developer | 0 comments

We recently migrated over to a UK leading web hosting infrastructure which involved migrating a large number of websites from one web server to another, and we did this with zero downtime. Which meant that the business websites involved never suffered from lost traffic, sales or enquiries. This is not as straight forward as it sounds on the face of things and requires planning and careful implementation to ensure all data, databases, files, settings, configurations and more are transferred with ease. As this is a common problem for people I thought it would be good to document the steps we took which served us well. Depending on the server technology you are moving from and to will depend on how simple (or difficult) this will be for you to implement. These guidelines are generic so you should be able to take what you need from these and see how this fits in with your technology.

DNS Records

Depending on where your DNS records are setup, if you are using your current DNS records, if you are using new DNS records or something else – will fully depend on if this is relevant for you.

If your current name servers are set to your old hosting provider such as ns1.your-web-host.com and ns2.your-web-host.com then this makes life a little simpler for you. When the time is right, you can simply point your domain names at the new web server by changing the name servers to ns1.your-new-web-host.com and ns2.your-new-web-host.com. That said, many people prefer branded name servers, such as the ones we run for ns3.contradodigital.com and ns4.contradodigital.com. This causes a few more challenges when migrating branded name servers.

If you are wanting to migrate branded name servers then you need to set up an interim stage. For us, our old branded name servers were set up as ns1.contradodigital.com and ns2.contradodigital.com which pointed to the old DNS server (a specific IP address) which then handled the traffic to websites with these name servers and pointed this traffic to the correct web server. If we were to simply migrate the DNS server IP address for ns1.contradodigital.com and ns2.contradodigital.com over to the new DNS server, this would take time to propagate, up to 48 hours which could cause inconsistent behaviour for users accessing websites listed.

Instead, by setting up new name servers which point to the new DNS server we can have ns3.contradodigital.com and ns4.contradodigital.com which can then propagate throughout the Domain Name System until we are ready to officially migrate the websites over. Once we are confident that the new name servers have propagated (see http://dnswatch.info to check) we can then begin the migration.

Beyond this, if you have any A, TXT, MX records or other that are configured on your old server, then make sure these are migrated too.

Transfer Data

Getting all of your data, files, databases, settings and more from your old web server over to your new website can be a challenge. Thankfully for us, we use a leading web server management system, cPanel which comes with a handy little transfer tool. This allows the old and new servers to talk to each other and automatically migrate everything over. This setup does require that you have SSH Root access to both servers, which you may or may not have depending on the old technology you are using.

If you are migrating between different web server control panels then this is going to be a much more manual process and often requires a detailed checklist to make sure you have transferred everything correctly and it has been implemented correctly on your new system.

It is important to reiterate this, but make sure you have transferred absolutely everything on your web server. To give you an idea this could include; files, redirects, email forwarders, distribution groups, emails, databases, FTP accounts, user logins, server logs (if needed) and more. Depending on how much of the functionality you use on your old and new webserver will depend on the areas that you need to check over. Always by over cautious to make sure you have checked everything since if you miss anything then you are unlikely to be able to recover this once you have cancelled the subscription on your old web server.

Website Migration

Once you have successfully migrated all of your data, it’s time to start migrating your websites to run from the new server and get rid of the old server. To start things off, start with a non-descript website if possible to make sure that the process has worked for your individual settings. The details above are specific to what we did and may or may not work for you. The final step is to switch your name servers so your domain names will be looking at your new web server instead of your old one.

Once you have updated the name servers for the test domain, then you can check that everything is working correctly before migrating the remaining domains on the system. This process will allow you to migrate your web servers seamlessly with zero downtime. This is a little more challenging for large scale ecommerce websites due to data continuity related to transactional data, but this is a little outside the scope of this blog post as this again depends on the technology being used related to the ecommerce setup.

Nuances

A few other points to note about web server migration is that you can trip up if you are migrating to servers with different versions of software running (PHP for example), different file systems, different operating systems, different access rights and more. When upgrading your web server, you are likely moving away from technology that isn’t suitable for your needs anymore or is limiting in some way. This causes a few problems naturally which may need to be overcome. You may also have some specific technology, non-standard and inaccessible server settings configured on your old server which can easily be missed during the migration. To avoid tripping up on some of these issues, it is always recommended to speak with your current web host to understand the full technical setup and software that is installed to make sure you have everything installed on the new server that is needed to support the websites and web applications that you are running.

Summary

The information outlined worked for us. It may not work for you. Understand the technology you are working with, in terms of what you are moving from and what you are moving to. If you are in any doubt, get in touch and we can help you with this process. Working with industry leading web hosting solutions means that we have a lot of experience working with great solutions, and also very poor solutions that people are migrating away from.