Efficient scalable I/O scheduling

A non-transitory computer-readable storage medium storing computer program modules for selecting and dispatching an input/output (I/O) request from a set of I/O requests for a plurality of clients, the I/O requests specifying read or write from storage volumes for the clients, the storage volumes stored on a shared storage device, the storage volumes further having guaranteed minimum I/O rate requirements, the computer program modules executable to perform steps comprising:

• determining a storage volume to service, which comprises:
• determining whether an actual disk throughput of I/O requests for the shared storage device exceeds a first threshold rate that is based on and exceeds a reserved disk throughput for the shared storage device, wherein the reserved disk throughput is a rate of I/O requests necessary to meet the guaranteed minimum I/O rate requirements for the storage volumes stored on the shared storage device;
• responsive to determining that the actual disk throughput exceeds the first threshold rate, selecting the storage volume to service based on credits for the storage volumes or based on priority for the storage volumes;
• and
• responsive to determining that the actual disk throughput does not exceed the first threshold rate, selecting the storage volume to service based on the guaranteed minimum I/O rate requirements for the storage volumes stored on the shared storage device;
• determining an I/O request queue associated with the determined storage volume;
• retrieving an I/O request from the determined I/O request queue;
• and
• sending the retrieved I/O request to a persistence layer that includes the shared storage device.

A system for selecting and dispatching an input/output (I/O) request from a set of I/O requests for a plurality of clients, the I/O requests specifying read or write from storage volumes for the clients, the storage volumes stored on a shared storage device, the storage volumes further having guaranteed minimum I/O rate requirements, comprising:

• a non-transitory computer-readable storage medium storing computer program modules executable to perform steps comprising:
• determining a storage volume to service, which comprises:
• determining whether an actual disk throughput of I/O requests for the shared storage device exceeds a first threshold rate that is based on and exceeds a reserved disk throughput for the shared storage device, wherein the reserved disk throughput is a rate of I/O requests necessary to meet the guaranteed minimum I/O rate requirements for the storage volumes stored on the shared storage device;
• responsive to determining that the actual disk throughput exceeds the first threshold rate, selecting the storage volume to service based on credits for the storage volumes or based on priority for the storage volumes;
• and
• responsive to determining that the actual disk throughput does not exceed the first threshold rate, selecting the storage volume to service based on the guaranteed minimum I/O rate requirements for the storage volumes stored on the shared storage device;
• determining an I/O request queue associated with the determined storage volume;
• retrieving an I/O request from the determined I/O request queue;
• and
• sending the retrieved I/O request to a persistence layer that includes the shared storage device;
• and
• a computer processor for executing the computer program modules.