In a selective logical-volume swapping process, a subset of storage
devices in a storage system are selected that represent good candidates
for swaps that will improve system performance. Workload statistics are
utilized from a number of sample intervals in a relatively long analysis
interval. The workload statistics are aggregated over intermediate
intervals of each analysis interval to yield a set of aggregated
statistics much smaller than the set of workload statistics. Based on the
aggregated statistics, a service processor searches for swaps of logical
volumes, ranks the swaps according to expected system performance
improvement, and selects source and target storage devices of the
higher-ranked swaps. The service processor can then perform a full
optimization analysis for this subset of storage devices utilizing the
workload statistics from all the sample intervals. More efficient use of
processing resources is achieved through the use of the smaller set of
aggregated statistics to identify the subset of devices for which full
analysis is performed.