Closing the business continuity gap
Clustering technology
Historically, such approaches have depended on clustering technology. Clustering allows several machines to run the same copy of the application which is accessing its data on shared storage. Clusters may consist of multiple physical and/or virtual machines and provide a platform that protects against physical or virtual machine failure. In some situations, it may also address availability for planned operations where individual machines in the cluster may be disconnected, allowing maintenance to take place.
The limitations of cluster centric approaches relate to application and processor failure. Failure situations that address the whole site, such as natural disasters, power outages and facility upgrades are not covered. Because clusters rely on shared storage and shared facilities, it is important to guard against failures at that level. In turn, this means protecting the storage from being a single point of failure. This can be costly, requiring storage virtualisation and/or replication to be implemented concurrently. Additionally, virtual clusters may suffer from corruption of shared application images.
Provisioning applications across machines from the same virtual image will not guard against application corruption, and not allow application maintenance, thus limiting the level of high availability that can be delivered.
As mentioned in the introduction, there is an increasing realisation that there is a disconnect between the reliance of the businesses on business critical applications and the IT approach to business continuity. The business continuity gap exists because the solutions discussed above ignore the needs of the end-user- uninterrupted access to applications regardless of the cause of failure.
Continuous availability
Results of a recent survey indicate that in regards to email, over half of organisations depend on the users to notify IT of an issue. By this time, email access has been interrupted. Addressing the needs of the user has resulted in a new discipline of continuous availability.
Continuous availability solutions typically use redundancy of data and hardware, combined with data replication, in a “shared nothing” approach. While replication solutions share this approach, the difference comes when looking at the impact on the user, and hence the business. Continuous availability solutions will provide pro-active application awareness.
Application availability will be monitored through embedded best practice facilities with a degree of self-healing provided, changes in application configuration and data dependencies will be catered for, and automation will be an option to avoid the need for manual intervention. The level of protection will embrace the end-to-end service, not just an individual software component such as Exchange.
The choice of availability strategy will depend on many factors. Taking into account complexity in operation, total cost of ownership, skills available and the risk to the business of failure may mean combinations of the above technology are required to address business risk.
—Nick Ogle is Regional Sales Director for Neverfail Group (www.neverfailgroup.com) in Australia.
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