1. A method of maintaining a fixed Quality of Service (QoS) for a Peripheral Component Interconnect Express (PCIe) storage device in relation to multiple hosts accessing the PCIe storage device, the method comprising: receiving a plurality of commands from the hosts in PCIe function queues of the PCIe storage device; fetching a subset of the plurality of the commands from the PCIe function queues, queuing the subset of commands in a first sequence according to a command arbitration policy established for the PCIe storage device, and storing the queued subset of commands in an internal memory of the PCIe storage device; retrieving the queued subset of commands from the internal memory as retrieved commands in a second sequence determined by applying a calculated QoS to at least one of the queued subset of commands; allocating PCIe device resources to an allocation of PCIe device resources based on payload information corresponding to each one of the retrieved commands; determining an execution time for each one of the retrieved second commands; pushing at least one of the retrieved commands to a wait queue; and calculating the calculated QoS for at least one command included in a combination of the queued subset of commands and the at least one command pushed to the wait queue following the determination of the execution time.