Many companies seek to have their information systems available to their customers at all hours of the day or night. This typically means that key technical personnel must remain on call perpetually, and be able to respond to emergencies on short notice. Then, when a server problem is detected, rapid response is mandatory.
In spite of rapid response by reliable DBAs, there will typically be significant downtime in case of a server failure. This lapse has led DBAs and System Administrators to consider cost-effective ways to meet a 24x7 uptime requirement. Especially attractive would be some option that could automatically detect and recover from a server disaster. It would also be best to avoid creating custom solutions that rely on unproven scripts or monitoring programs.
These stringent requirements are addressed by an architecture commonly called “HA,” for High Availability. Veritas Cluster Server, or VCS, is one example of an HA system. The goal of all HA systems is the same: minimize downtime due to server failure. The type of technology used in these HA systems is not new, nor is it especially exotic. Many corporations requiring 24x7 availability use VCS or a similar product. Other examples of HA systems are HP MC Service Guard and IBM HACMP. Although this paper emphasizes the Veritas HA product, many of the principles described here are equally applicable to the HP and IBM products.
OVERVIEW OF VCS
As shown in Figure 1, a typical cluster has two nodes. VCS requires that a “service group” be defined for each database and associated applications. Each service group contains everything that is relevant to that particular database and application. Then, when failover occurs, everything in that Service Group transfers to the other node
For instance, in Figure 1, Service Group “A” contains a database, certain areas on the shared disk, and a “Virtual” IP address, or VIP. This VIP points... [continues]
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(2009, 12). Vcs Clustering. StudyMode.com. Retrieved 12, 2009, from http://www.studymode.com/essays/Vcs-Clustering-265588.html
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"Vcs Clustering." StudyMode.com. 12, 2009. Accessed 12, 2009. http://www.studymode.com/essays/Vcs-Clustering-265588.html.