A number of services can be clustered. Microsoft Exchange Server supports clustering;
you can also use clustering to support a file server. However, it??™s important to
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understand that all clustering operations sit on top of Microsoft Cluster Server (MSCS).
With earlier versions of MSCS, the installation and the actual clustering functions didn??™t
work so well. With each progressive version, things have become simpler and more
robust, both with clustering itself and with SQL Server??™s use of clustering.
Clustering Architecture
Any cluster architecture has three base requirements: two identical servers and some sort
of shared storage between them. The shared storage is usually either an external SCSI
cabinet or a SAN. Both servers have a network card for outside access (that is, for users
accessing the cluster), and in the best-case scenario, a second network card dedicated to
internal communications between the two servers, as shown in Figure 7-1.
Figure 7-1. A minimal clustering configuration
The main goal of a clustered architecture is for one server to take over all operations
if the other server should fail.
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