A method for operating a computer data storage system is described. A plurality of requests are received from a client, each request of the plurality of requests having assigned a unique sequence number, each request being an input/output request to a data storage device. The plurality of requests is divided into a plurality of subsets of requests. A unique batch number is assigned to each subset of requests so that each subset of requests is assigned a unique batch number. A first subset of requests having a first batch number is executed in arbitrary order with respect to the sequence number of each request. A second subset of requests is executed in response to a second batch number after execution of all of the first subset of requests has completed.