Performance impact of queuing on the storage array and host

There are several storage queues:

  • Device driver queue
  • Kernel queue
  • Storage array queue

The device driver queue is used for low-level interaction with the storage device. This queue controls the number of active commands that can be on a LUN at the same time. This number is effectively the concurrency of the storage stack. If you set the device queue to 1 then each storage command becomes sequential.

The kernel queue is an overflow queue for the device driver queues. This queue enables features that optimize storage (it doesn't include them; they are built using the queue). These features include multi-pathing for failover and load balancing, prioritization of storage activities, which is based ...

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