Techniques are described herein for accurately measuring the reliability of storage systems. Rather than relying on a series of approximations, which may produce highly optimistic estimates, the techniques described herein use a failure distribution derived from a disk failure data set to derive reliability metrics such as mean time to data loss (MTTDL) and annual durability. A new framework for modeling storage system dynamics is described herein. The framework facilitates theoretical analysis of the reliability. The model described herein captures the complex structure of storage systems considering their configuration, dynamics, and operation. Given this model, a simulation-free analytical solution to the commonly used reliability metrics is derived. The model may also be used to analyze the long-term reliability behavior of storage systems.