We migrate all the data on the live server to the new server without making the new server live right away. We then send you instructions on testing your websites on the new server, which involves tricking your testing computers DNS into thinking the domains are hosted on the IP addresses of the new server. When you are happy things are working correctly, you give us a time and date to go live with the switch, often during the middle of the night or on the weekend when server traffic levels are lower. At that time, we perform a final fast data sync, copying over files and databases that were altered or newly added since the initial data transfer, so no data is lost since the initial migration. If the new server is not retaining the old server’s IP addresses, we change DNS to point to the new server’s IP addresses. Otherwise, we have the data center swap the IP addresses causing the new server to go live. In this case, there is very minimal downtime if any. When changing DNS, downtime is limited for the time it takes the DNS change to propagate. If DNS propagation time is of concern, you can ask us to change the DNS TTL (time to live) for all your domains to be 5 minutes at least 24 hours before the switch is made. This will prevent DNS servers on the Internet from caching the DNS for your domains longer than 5 minutes and the IP change will be seen very quickly after the migration. If you ask us to lower the TTL before the migration, be sure to ask us to raise it to 24 hours after the migration. This is proper Internet etiquette and lowers the amount of DNS queries your server has to perform each day.