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Information in the form of data represents a significant portion of valuable corporate assets. Because data ultimately resides on disk arrays and tape, the safeguarding of storage is a key component of business continuity and disaster recovery. As with tape backup projects, though, working on a disaster recovery strategy is a kind of purgatory — not quite hell, but a far cry from heaven.
Aside from the technical challenges, no one likes to dwell on all the bad things that can happen to human and IT corporate assets, or imagine all the steps required to recover essential data and resume operations during a disruption. Most of all, people do not want to consider what would happen if enterprises simply collapsed due to nonexistent, inadequate, or untested DR solutions.
Despite decades of procrastination on disaster recovery projects, companies are finally beginning to recognize the exposure they bear if they do not have a well-conceived and implemented disaster recovery plan for storage. Fortunately, recent technical developments on the DR front have resulted in more flexible and economical solutions that enable customers to implement high availability storage strategies even under the constraints of tight budgets. Compared to legacy DR technologies, these new solutions provide significant savings in both hardware and communications costs, and offer more flexibility to provide different levels of data redundancy that meet the requirements of diverse business applications.
Sizing the DR Tactic to Business Requirements
While all corporate data has some value, not all of this information is essential to the immediate resumption of business in case of disaster or outage. One of the first steps in implementing an effective DR strategy, then, is to prioritize data and match data types to levels of recovery.
Online transaction processing, for example, may need a current and full copy of data available in the event of disruption. This requirement is generally met through synchronous disk-to-disk data replication over a suitably safe distance. In contrast, for application development code, it may be sufficient to have tape backups available, with restoration to disk within 2-3 days time. Sizing the DR tactic to business requirements helps keep DR costs under control while streamlining a recovery process.
The hierarchy of data availability begins with solutions based on server clustering and synchronous disk data replication. Geoclustering, or the ability to have servers in multiple locations assume the tasks of failed servers, ensures non-disruptive access between network clients and server assets.
Synchronous disk-to-disk data replication ensures that the backup copy of data is current to the most recent transaction (write to disk). The combination of clustering and synchronous replication enables transparent failover from a production site to a backup site, regardless of whether individual server or storage devices fail.