queue depth

Queue depth, in storage, is the number of pending input/output (I/O) requests for a volume.   

Performance-demanding applications can enough generate storage I/Os to create queue depths in the hundreds. Adding more spinning hard disk drives can be somewhat effective in improving response time, but the cost of the drives can negatively impact the budget and all those extra drives will take up physical space in the data center.  Solid-state drives (SSDs), on the other hand, have virtually no latency and respond almost instantly to I/O requests.  In some cases, a single SSD can eliminate a queue depth that would take hundreds of hard disk drives to service.

This was last updated in January 2012

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