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 Andréa Skov discusses the key considerations for selecting the right email continuity system.
In today’s business world, email has become firmly established as a mission critical application. System downtime, therefore, results in tangible implications from lost revenue opportunities, missed contractual obligations, and reduced employee productivity. Adding to this are the significant, and often immeasurable, costs related to erosion of customer goodwill and job jeopardy for IT personnel. Andréa Skov of Teneros discusses the key considerations for selecting the right email continuity system.
An email server failure can occur at anytime. When it does, users expect full email functionality and data access to be restored within seconds on the continuity solution. However long the failover, full email functionality is imperative. To achieve this, organisations must evaluate the type of user experience that an email continuity solution needs to provide during a failover scenario.
Managing the user experience
Two factors determine the user experience: client transparency and full Exchange ecosystem support.
It is critical for business users to have seamless and full-featured use of their normal email clients during failover. Email continuity solutions that provide only a limited Outlook feature-set during failover or which don’t support cached or online mode clients can lead to significant support issues as well as interruptions in critical business processes. Before choosing a continuity solution, it is important to verify whether native and full Outlook support is available, without exceptions.
As Microsoft Exchange is the platform for a number of mission critical business applications, it is important to verify that the email continuity solution selected supports the critical Exchange eco-system applications that are being used in your business. The email ecosystem applications must continue to work seamlessly during an email server failover both to maintain end users productivity and to assure regulatory compliance.
Returning to normal
But be aware: the problems aren’t all over once the users’ experience has been attended to. Returning production to its original location is the most complex operation in the email continuity scenario. If improperly done, failback can result in data loss, significant bandwidth utilization, days of manual IT labour and email downtime.
To counter these challenges requires a number of critical factors including: divergent database resolution, no reseeding and no single point of failure.
One key challenge in performing painless WAN failback for database applications, such as Exchange, is resolving divergent databases. Data in the primary and secondary Exchange servers can diverge resulting in unreplicated email data present on the primary Exchange server and new email data generated on the secondary Exchange server which is then not present on the primary Exchange server. During failback, these databases need to be reconciled with no loss or damage to data in either server. The only way to address this situation is to synchronize the mail objects on both servers. This feature is provided on continuity solutions that offer object-level replication APIs in Exchange and underpins the success of an appliance that automatically detects divergent databases and resolves them into a single, complete database without data loss.
Another aspect of the recovery process is reseeding which refers to replicating the entire email database from the disaster recovery site server to the primary site server or vice versa. Many of the solutions in the market require reseeding the entire database during failback which can lead to data loss as well as being a significant drain on bandwidth and time. Therefore, always check with the continuity vendor if reseeding is actually required. While often necessary, it can be avoided if a continuity solution provides a proprietary incremental failback capability plus differential reseeding where data is compared and automatically replicated without manual intervention.
Finally, it goes without saying that your email continuity solution must not have a single point of failure. This is defined as hardware, software or a logical data component that can cause the whole continuity solution to cease operation. The only way to address this situation is to synchronize the mail objects on both servers using object-level replication technology. Any sequential replication method, such as disk block replication or log replication, will not address this issue without data loss.
Without a doubt, selecting the right email continuity solution for Exchange 2007 can be a confusing, challenging task because of the intricacy of the details. So, be wary of generic solutions, such as disk replication or virtual machine failover, which are not built to be Exchange specific, application aware continuity solutions. They may appear less expensive in up-front cost, but will fail to provide the required functionality such as corruption protection during data replication or divergent database resolution on failback. Instead, seek out turnkey, application-aware solutions that offer the requisite mix of simple installation, ease of use, no ongoing maintenance burden, advanced availability features, and worry-free reliability.
http://www.teneros.com/
•Date: 7th Nov 2008• Region:World •Type: Article •Topic: IT continuity
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