Variable-RPM Hard Disk Drive Control

A computer-implemented method comprising:

• determining a first plurality of storage devices in a storage subsystem to include in a fixed set such that all data stored to the storage subsystem is available for input/output (I/O) requests from the first plurality of storage devices;
• preventing the first plurality of storage devices of the fixed set from transitioning between operational modes;
• determining an I/O workload of an identified storage device in the remaining storage devices in the storage subsystem not in the fixed set;
• determining whether the I/O workload satisfies a threshold;
• and
• responsive to determining the threshold has been satisfied, transitioning an operational mode of the identified storage device.

A computer program product comprising a non-transitory computer useable medium including a computer readable program, wherein the computer readable program when executed on a computer causes the computer to:

• determine a first plurality of storage devices in a storage subsystem to include in a fixed set based on a fault tolerance scheme such that all data stored to the storage subsystem is available for input/output I/O requests from the first plurality of storage devices, wherein the computer readable program causes the computer to prevent the first plurality of storage devices of the fixed set from transitioning between a high revolutions per minute (RPM) RPM operational mode and a low RPM operational mode and to allow remaining storage devices in the storage subsystem are configured to transition between the high RPM operational mode and the low RPM operational mode;
• determine an I/O workload of an identified storage device in the remaining storage devices in the storage subsystem;
• determine whether the I/O workload meets a threshold;
• and
• responsive to determining the threshold has been met, transition an operational mode of the identified storage device from the high RPM operational mode to the low RPM operational mode.