Patent ID: 7957398

Claim:
A method for selecting a path by which to send an I/O request from a host to an associated storage subsystem from among a plurality of paths from the host to the associated storage subsystem, the method comprising: identifying, for each of the plurality of paths, a first limitation on a traffic level for I/O requests having a first urgency level, wherein the first urgency level does not comprise the highest urgency level; tracking a first metric corresponding to the first limitation for each of the plurality of paths; identifying a first set of paths whose first metric does not exceed its first limitation; and transmitting a first I/O request having the first urgency level by one of the first set of identified paths; associating the first I/O request with one of a plurality of I/O groups, each I/O group comprising I/O requests sharing a distinguishing characteristic; identifying a performance target for each I/O group; tracking, for the first I/O request, a metric corresponding to the performance target for the associated I/O group; assigning an urgency level to the first I/O request based on the difference between the performance target and the metric, wherein when the metric is approximately equal to or greater than the performance target, the highest urgency level is assigned to the first I/O request.