Abstract: Embodiments are directed to a requirements-based performance monitor (RBPM) that presents users, through a command line interface or graphical user interface, with a single number in the range of 1-100% and/or a color-coded indicator that allows users to readily tell if the I/O needs of their primary applications in a virtualized computing system are being sufficiently satisfied. The RBPM takes into account both device latency, throughput, IOPS, and slow I/O measurements and primary application requirements. The process uses detailed device latency tables for each device to allow a user to find the particular device and time that performance degradation occurred.