title: automatic failover if webserver is down (SRV / additional A-record / ?)
body: <p>I am starting to develop a webservice that will be hosted in the cloud but needs higher availability than typical cloud SLAs provide.</p>
  
  <p>Typical SLAs, e.g. Windows Azure, promise an availability of 99.9%, i.e. up to 43min downtime per month. I am looking for an order of magnitude better availability (&lt;5min down time per month). While I can configure several load balanced database back-ends to resolve that part of the issue I see a bottleneck at the webserver. If the webserver fails, the whole service is unavailable to the customer. What are the options of reducing that risk without introducing another possible single point of failure? I see the following solutions and drawbacks to each:</p>
  
  <ol>
  <li><p>SRV-record:
  I duplicate the whole infrastructure (and take care that the databases are in sync) and add additional SRV records for the domain so that the user tying to access www.example.com will automatically get forwarded to example.cloud1.com or if that one is offline to example.cloud2.com. Googling around it seems that SRV records are not supported by any major browser, is that true?</p></li>
  <li><p>second A-record:
  Add an additional A-record as alternatives. Drawbacks:
  a) at my hosting provider I do not see any possibility to add a second A-record but just one... is that normal?
  b)if one server of two servers are down I am not sure if the user gets automatically re-directed to the other one or 50% of all users get a 404 or some other error</p></li>
  </ol>
  
  <p>Any clues for a best-practice would be appreciated</p>
  
  <p>Cheers,
  Sebastian</p>