The current document is directed to methods and subsystems within computing systems, including distributed computing systems that efficiently store metric data by approximating a sequence of time-associated data values with one or more linear functions. In a described implementation, a running variability metric is used to control variation within the metric data with respect to the approximating linear functions, with a variation threshold employed to maximize the number of data points represented by a given linear function while ensuring that the variation of the data with respect to the given linear function does not exceed a threshold value. In one implementation, the metric data occurs within a graph-like configuration-management-database representation of the current state of a computer system.