Up-Time All the Time: Designing GIS for High Availability

Introduction
GIS has expanded into the information mainstream as a core enterprise technology. As organizations re-engineer core applications to be spatially enabled, and as the whole enterprise becomes spatially enabled, we are witnessing rapid growth in the amount of spatial data and in the number of GIS users. And as GIS integrates what used to be islands of data into large – sometimes tens of terabytes! – enterprise databases housing both spatial and tabular data, the domain of mission-critical applications expands to spatial applications.

With these changes come several major challenges: GIS data and applications are being treated as a corporate resource, just like more traditional IT implementations; and spatial applications are now commonly subjected to many of the same design principles as traditional enterprise-wide, mission-critical applications. But computer hardware can fail, and such failures are costly to an organization if mission-critical applications cannot be kept running effectively – that is, “available”.

GIS user applications are "available" only if they allow users to access the GIS server applications and the GIS data files. High Availability environments are designed for computing installations that require critical systems to be automatically and seamlessly restarted in the event of a hardware failure. They can ensure that data remains accessible, and that applications can be kept running, even during a prolonged hardware failure.

This paper will investigate the nature and architecture of a High Availability GIS: the use of standard hardware and software components to provide automatic failover and continuous operation in the event of system failure. It will describe new features of the Tru64 UNIX operating system and TruCluster software from Compaq Computer Corporation that automatically enable this functionality in any supported application environment. At the same time, it will demonstrate how High Availability was earlier implemented by two major GIS software vendors on the Compaq AlphaServer platform, to minimize interruptions to applications and to keep file systems continuously available.