Patent ID: 7817562

Claim:
A method, comprising: determining a quality of service for virtualized storage elements in a virtual storage system that provides abstraction of logical units and a plurality of storage elements for a host application, by: initiating an I/O request to a first one of the plurality of storage elements within the virtual storage system; measuring a time the first one of the plurality of storage elements takes to respond to the I/O request; reporting a measure of the quality of service available from the first one of the plurality of storage elements; using an estimation of a relationship of a service time and a size of an I/O request to determine a reserve capacity of the first one of the plurality of storage elements based on the time the first one of the plurality of storage elements takes to respond to the I/O request; and using a known relationship between a size of an I/O request and a service time with a known number of outstanding I/O requests to predict a service time for a larger I/O request based on a service time for a smaller known I/O request.