Vertical fault isolation in a computer system

The majority of Internet outages are directly attributable to software upgrade issues and software quality in general. Mitigation of network downtime is a constant battle for service providers. In pursuit of "five 9's availability" or 99.999% network up time, service providers must minimize network outages due to equipment (i.e., hardware) and all too common software failures. Service providers not only incur downtime due to failures, but also incur downtime for upgrades to deploy new or improved software, hardware, software or hardware fixes or patches that are needed to deal with current network problems. A network outage can also occur after an upgrade has been installed if the upgrade itself includes undetected problems (i.e., bugs) or if the upgrade causes other software or hardware to have problems. Data merging, data conversion and untested compatibilities contribute to downtime. Upgrades often result in data loss due to incompatibilities with data file formats. Downtime may occur unexpectedly days after an upgrade due to lurking software or hardware incompatibilities. Often, the upgrade of one process results in the failure of another process. This is often referred to as regression. Sometimes one change can cause several other components to fail; this is often called the "ripple" effect. To avoid compatibility problems, multiple versions (upgraded and not upgraded versions) of the same software are not executed at the same time. The invention provides a method for fault isolation in a computer system, such as a network device. The method calls for providing a plurality of modular processes, and forming groups, based on hardware in the computer system, of one or more of the plurality of modular processes. A fault within a group is detected, and recovery from the detected fault is accomplished without affecting processes or hardware in other groups.