Which of the following describes the theoretical maximum number of operations a disk can perform and is used to denote the disk performance of storage tiers?

IOPS (Input/Output Operations Per Second) directly measures the number of input/output requests a storage device can process in one second, making it the standard metric for disk performance. Higher IOPS indicate better disk performance, which is crucial for determining the suitability of storage tiers for different workloads.

QoS (Quality of Service) relates to managing network or storage resource allocation to prioritize certain traffic or workloads, not the maximum operations a disk can perform.

MIPS (Millions of Instructions Per Second) is a measure of a processor's speed, indicating how many millions of instructions a CPU can execute per second, not disk performance.

FPS (Frames Per Second) is a measure of how many unique consecutive images a display device can render per second, primarily used in graphics and video, not disk performance.