In order to detect problematic drives in random arrays of independent disks, the system measures the latency of executing command sets which are broadcast to all disks in the data storage system and the results are compared to identify which disks take substantially longer to complete the requests. Disks that take longer to complete requests are likely to be problematic and are candidates for further examination and replacement. The disks in each tier group are compared to determine if any disk in that group exhibits problems. Also, counters for each tier group are compared to determine if the problem is with the disk or with the channel of the tier group. The latency of each disk in the tier group is saved in a table to provide a histogram of the latency of the disks in the tier group. Histograms of the disks in a single tier group are compared to determine if a specific disk is problematic. Histograms of each tier group are compared to determine if a specific disk is problematic or all the disks on the same channel exhibit problems.