With distributed filesystems, there is a single point of failure in that if the server (that owns the underlying storage) crashes, service is interrupted until the server reboots. In the event that the server is unable to reboot immediately, the delay in service can be significant.
With most critical business functions now heavily reliant on computer-based technology, this downtime is unacceptable. In some business disciplines, seconds of downtime can cost a company significant amounts of money.
By making hardware and software more reliable, clusters provide the means by which downtime can be minimized, if not removed altogether. In addition to increasing the reliability of the system, by pooling together a network of interconnected servers, the potential for improvements in both performance and manageability make cluster-based computing an essential part of any large enterprise.
The following sections describe the clustering components, both software and hardware, that are required in order to provide a clustered filesystem (CFS). There are typically a large number of components that are needed in addition to filesystem enhancements in order to provide a fully clustered filesystem. After describing the basic components of clustered environments and filesystems, the VERITAS clustered filesystem technology is used as a concrete example of how a clustered filesystem is constructed.
Later sections describe some of the other clustered filesystems that are available ...