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High availability can equal high cost
Like any other complex system, ensuring high availability for Exchange often doesn't come cheap. In general, redundancy forms the core of any high-availability product. As such, high availability essentially doubles the overall cost because there are two servers, two software licenses, two storage arrays and two communications links.
Citgo Petroleum figured it was looking at a minimum investment of $500,000 to completely replicate its Exchange environment for high availability. "Including all the hardware we would need--more disk, a new SAN--and SAN consulting, it would be at least a $500,000 project," estimates the firm's Swails.
Instead, the company opted for CA XOsoft's WANSyncHA (XOsoft was recently acquired by CA Inc.), which provides asynchronous replication and automatic failover for Exchange and other applications running on Windows servers. "XOsoft continuously replicates writes in small chunks," explains Swails. Citgo had to purchase an additional license of Exchange and added extra Windows servers, as well as some communications bandwidth (less than a T1 line). But the total cost was "less than 10% of the $500,000 we expected to pay," she reports.
This was first published in September 2006