A Host Bus Adapters (HBA) is a dedicated fiber-optic transceiver adapter to connect to Fibre Channel (FC) based storage networks. A FlashArray can be connected to a Hyper-V host via FC.
Physical HBAs have a tunable setting on the physical device called queue depth. The queue depth value specifies the number of I/O requests that the host will put into a queue for a target storage port. If the maximum queue depth is reached, the device will reject and discard additional commands, forcing the Hyper-V host to reissue the I/O request a short time later. This results in latency to the host and/or the VM. If this discard and retry occurs, the observed storage latency inside the Hyper-V VM will increase, potentially causing performance degradation for the workloads.
When switching to faster storage such as FlashArray, default queue depth values may need to be changed. If necessary, adjusting the queue depth to a higher value can help boost performance levels from the Hyper-V host and VM workloads. Increasing it too high can result in performance degradation from overloading the SAN controllers, as the ports might be unable to handle such a high rate of concurrent commands. All Hyper-V hosts connected to these ports could be negatively impacted.
Check with your HBA hardware vendor for the value of your HBA queue depths and adjustment process, and test accordingly with a combination of your application workload and synthetic benchmarking tools to find the right queue depth balance for your storage array.
A good reference to see how to tune FlashArray with FC-based implementations is the article “SAN Guidelines for Maximizing Pure Performance”.