There are two categories of application downtime: planned and unplanned. There are many causes for unplanned downtime including operational failures, application failures, component and system failures, site failures, and regional disasters. Companies who are vulnerable to natural disasters like hurricanes, floods, earthquakes have to worry about their disaster recovery site being sufficiently far away to provide protection from these more wide-spread natural disasters.

A Data Center survey done by Gartner shows that:

• 40% of the downtime is caused by operator errors which are people or process related. With increasing data center complexity, the incidence of operator errors is on the rise. So, any solution that simplifies the data center can help reduce the operator errors.
• Application induced failures also contribute to 40% of the downtime. With ever new functionality being added to an application, the number of lines of code in a software application grows, increasing the likelihood of bugs. So, it is important to be able to quickly recover from application crashes.
• Component & System failures are the next likely cause of downtime, but on the storage side all the top-tier enterprise storage vendors have addressed this problem with a highly available architecture.
• The likelihood of site disasters has risen lately with the incidence of terrorist activities as well as hacker threats from both inside and outside the company, in addition to more typical causes like power grid failure, fires, plumbing accidents. So, this can no longer be ignored by customers.

There are several considerations to be made when deciding which type of disaster recovery solution to implement:

• Which applications need protection? Not all applications are equal, so you need to tier applications based on their criticality and have different sets of RPO for each application tier.
• What is your RPO in case of a disaster? RPO defines the amount of time for which work may be lost in the event of an unplanned outage at the primary site. It is used to define how frequently data is replicated to the disaster recovery site. This frequency determines how much data loss an organization is willing to tolerate—less frequent replications translate into more data loss. A zero RPO implies no data loss, which can only be addressed by a synchronous replication solution. This requires a high-bandwidth network and can only mirror sites that can be no more than 100 km apart. If you can afford to go with a higher RPO, an asynchronous replication solution with RPO in minutes or hours is much more flexible and cost-effective and has the ability to provide coverage for more of your applications.
• What is your RTO in case of a disaster? RTO is how quickly you need to failover to a disaster recovery site —seconds, minutes, hours, days.

Metro Cluster

MetroCluster is a unique, cost-effective synchronous replication solution for combined HA and DR, protecting against site disasters within a campus or metro area.

MetroCluster highlights: