Techniques for processing I/O operations may include: receiving an I/O having an associated expected execution time (EET) and I/O service level; selecting, in accordance with the EET and service level of the I/O, a first I/O queue from multiple pending I/O queues; inserting the I/O into the first I/O queue; and performing I/O shifting. I/O shifting may include shifting I/Os from one pending I/O queue to another that is ranked immediately higher than the one pending I/O queue. The multiple I/O queues may be ranked from a highest priority queue to a lowest priority queue. I/O shifting may shift I/Os from the highest priority queue to execution and shifting I/Os from another queue into the highest priority queue. I/O shifting is subject to remaining credits available of the multiple I/O queues and time distance between source and target queues.
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