Same page, two servers, one address.

A load balancer sends each request for this site to one of two web servers. Both servers hold the same files, so you get the same page from either one.

The board above shows real values that your browser measured when it loaded this page.

Test the path

Your browser sends 20 requests, one after the other, with the cache off. Each tile shows the time for one full reply.

    The route

    The load balancer picks server A or server B for each request. The two servers send identical pages, so you can't tell which one answered. That is the goal: a visitor sees one site, even when a server goes away for maintenance or migration.

    How a migration moves

    1. Copy the site to both serversEach server gets the same files and the same settings.
    2. Add both servers to the poolThe load balancer checks each server and sends traffic only to healthy ones.
    3. Test each server directlyEach server must answer on its own before it takes public traffic.
    4. Point the address at the load balancerDNS sends visitors to the load balancer instead of to one server.
    5. Watch, then retire the old pathWhen traffic is steady and no requests fail, remove the old server.