Mistake #8 is not having adequate system resources to run applications in failover. Your business continuity depends on your ability to switch over to a mirrored, real-time version of your production site. Anything less can put your business at risk for extended downtime. Trying to fail over your applications to an older version of your production environment may seem like a reasonable approach for saving money, but you will probably find that the old environment does not have the capacity to support your new applications. In this case, your applications will fail, putting business transactions at risk.
If you’re going to make an investment in high availability to protect your production site, be sure that the high availability solution provides end-to-end replication in real time of that production site in order to guarantee business continuity and ROI.