Does Your Failover Hosting really Fails Over?

For truly mission critical and important sites that demand round the clock availability, fail over hosting is the way to go. But what exactly is failover hosting? – It simply means that your site is available on more than one server and in an event where the site becomes unavailable on the first server, the second server will continue to serve your site. This is failing over from first server to second. Of course, failover architecture can be designed and implemented in several ways but in reality the fail over should actually be transparent to end users who are accessing the website.

If you were to extend the failover architecture a little bit, it would become failover plus load balanced hosting where both the servers will serve your website and depending on the load on the first server, the second server starts serving the web pages. If the first server goes down, the entire load falls or fails over onto second server.

Fail overs are of two types. Manual and Automatic. Manual failover is certainly not an option to consider as it serves no purpose other than bringing your site back online from the second server but the downtime is transparent to the user and they could clearly see that your site has been down. In case of an automatic failover, as soon as your site becomes unavailable on the first server, the second server will start serving the site. A simple and automatic failover hosting could be monitoring the port 80 and/or other ports for their availability on the first server and as soon as those ports stop responding, the DNS or nameserver should start redirecting the site to the second server. It’s much easier to write this than implementing it in real time.

Some hosting providers use hardware to detect availability of sites on the first server and based on the response, requests are redirected to the second server. One such hardware is from F5. There could be other hardware solutions available but by far F5 devices have been one the most widely used for such tasks. They are pretty expensive but offer high return on investment.

Having said all that about failover hosting, ensure that you consider the following points before you signup with any failover hosting plans.

• The failover type should be fully automatic.
• It must be transparent to end users.
• The second server should have same hardware specs as the first one. This ensure that if the first server faces a hardware failure, performance of the site will not be affected when it is served from the second server.
• Ask your provider if they test their failover architecture from time to time. There are many patched that are installed on the server and one or two of them could have significant impact on availability depending on how the failover was designed.

If you need any help with making a decision about hosting, don’t hesitate to contact me.