Patent ID: 7437727

Claim:
A method for accessing data on a storage system comprising: defining a data access request in terms of a plurality lower level I/O tasks, the lower level I/O tasks each performing an operation used in servicing the data access request, wherein each I/O task of the plurality of lower level I/O tasks is an asynchronous I/O task that is scheduled independently from other I/O tasks of the plurality of lower level I/O tasks; assigning resources dynamically to a first I/O task, wherein the resources are organized in a hierarchical order; executing the first I/O task of the data access request while preventing execution of I/O tasks with resources higher in the hierarchical other than the resources assigned to the first I/O task; and executing a second I/O task, wherein the second I/O task is assigned a resource lower in the hierarchical order than the resources assigned to the first I/O task while the first I/O task is pending.