Downtime during a move is avoidable with sequencing rather than luck.
THE PRINCIPLE
Never take anything down until its replacement is proven to work. Both servers should be capable of serving the site during the switch.
THE STEPS
- Build or restore the site on the new server while the old one keeps serving.
- Lower the TTL on your DNS records to 300 seconds at least 24 hours before the switch. This makes propagation fast when it matters.
- Test the new site thoroughly using your hosts file. Check every important page, forms, checkout and the admin area.
- Create all email mailboxes on the new server in advance.
- Freeze content changes on the old site shortly before the switch, so nothing is written to a database you are about to abandon.
- Do a final database sync if content changed after your copy.
- Switch the nameservers.
- Keep the old server running for at least a week.
- Monitor both for incoming email during the transition.
FOR SHOPS AND ACTIVE SITES
Schedule the switch for your quietest hours and put the site in a brief maintenance mode during the final database sync, so no order is written to the old database after the copy.
