When migrating from shared hosting to semi-dedicated hosting, or higher (such as a VPS), your site will need to be moved from one server to another. This article will try to explain the process and steps involved in doing this so you can have a better idea of what to expect during the migration period.

The Process

1. We first transfer the account from one server to the other using the built-in cPanel transfer tool. This tool allows is to quickly and easy move an account and its entire contents to another server, without missing a single file or account setting. Essentially the account is a direct copy of the old account and as a result of this your data will be identical.
2. We utilise the 'express transfer' option within cPanel which automatically updates our DNS records to point your domain name(s) to the new server. This is done to speed up the migration and to ensure that new visitors start accessing the site as quickly as possible. If your name servers are not set to ours, you will need to update your DNS to the IP address we send you via e-mail yourself. The sooner you do this, the sooner the migration can complete. If you are already using our name servers then no changes are necessary on your part.
   
   DNS propagation (the act of waiting for everyone to get the new IP address to your site) can take up to 24 hours, or more in extreme cases. Unfortunately this is unavoidable, as DNS is potentially cached at various different points in any connection. This cache is typically During DNS propagation some visitors may see your site on the old server, and some visitors will see it on the new server.
3. To prevent the situation where users may attempt to add content to your site (blogs, forums) or perhaps even attempt to generate orders through a site on the old server (eCommerce sites), we automatically disable access to dynamic scripts (PHP pages) on the old account. This means any visitors whose DNS has not yet updated and are still accessing the site on the old server will instead receive an "Account Moved" page. This page will inform them that the domain they are accessing has been moved to a new server and that their DNS is currently out of date. This page also provides instructions that visitors can potentially follow in order to try and speed up this DNS propagation so they can access the site on the new server.
   
   It is our experience that very few users will see this page, and that DNS propagation completes very quickly indeed. For clarification, the "Account Moved" page cannot be customised or styled on an account level and is a server wide default page implemented by cPanel. If you do not want this page visible on your old website or account then please let us know. Please be advised that by disabling the "Account Moved" page your visitors may continue to use your website to submit comments (if applicable), submit forum posts (if applicable) or even attempt to submit orders (if applicable). All of this information would be submitted on the old server and would not be accessible to you or your new site once DNS has propagated. For this reason we very strongly recommend that this page remain active on your account otherwise your data may become desynchronised.
4. The account on the old server is locked and access (via FTP and other methods) is disabled. This is to ensure that people do not make any changes to the old account that would then not be carried over to the new account recently migrated.
5. We will send you an e-mail/ticket update to confirm the migration process has completed and to provide you with the new IP address of your account. If your DNS or name servers are not pointing to us then you will be required to update these at the relevant providers as soon as possible. At this point you can access cPanel on the new server immediately via our client area. Once we have migrated the account to the new server, you will no longer be able to access any data or information on the old server and instead will be reliant on the new server only.
6. Your old account is kept active on the old server for at least 72 hours to ensure there are no problems on the new server. After at least 72 hours and if no issues are reported, your old account and its data and settings are permanently removed from the old server. At this point your account and domain(s) will be loading from the new server and DNS should have fully propagated for everyone.

Terminology
DNS Propagation is the term used to describe the process of DNS updating throughout the Internet. When you make a change to DNS, other servers on the Internet need to pick up and detect these changes so they know where to correctly load a website from. This process is not instant, and is directly related to DNS caching (more information on this below). Usually the act of propagation is very quick (within hours) but for safety we always recommend to allow up to 24 hours, or perhaps more in some extreme cases. How long this exact process takes depends mostly on factors outside of ThisWebHost's control.

DNS Cache/caching is the act of taking a DNS response and saving it somewhere to improve performance. When accessing a website your computer will check the name servers on a domain and then ask those servers "What is the IP address for this site?" - this is how DNS works. Once the servers respond with the IP address, your computer will save that response somewhere so that it doesn't have to keep asking "What is the IP address for this site?" every time you access it. This cache (the saved result) is updated every so often (usually hours), but will not instantaneously update as soon as an IP address is changed for a domain. The time between how often this "cache" updates is referred to as propagation (as above).