1. A computer-implemented method of adjusting committed rates for customers of shared resources, comprising: under control of one or more computer systems configured with executable instructions, receiving a request to adjust a committed rate of input/output operations per second (IOPS) for at least one data volume in a data environment, the request capable of specifying an adjusted committed rate corresponding to any portion of a capacity of one or more servers for the at least one data volume, the request being received as a Web service request to at least one application programming interface (API); if the request relates to decreasing the committed rate: reducing a rate commitment for at least one server for the at least one data volume for the customer; if the request relates to increasing the committed rate: determining at least one server having available committable rate capacity in the data environment, the at least one server capable of including at least one server for which the customer already has a committed rate; and committing at least a portion of the available committable rate capacity of the determined at least one server to the obtain the increased committed rate for the customer request; and storing information for the at least one server and the adjusted committed rate to a data store.