Storage Devices FAQ

Q What is queue depth?


A The number of simultaneous requests on a drive's request queue.
When an application requests data from a disk controller, the controller is responsible for fetching the data from the physical drive. Assuming there is just one request for data outstanding the controller will simply fetch the data and return it to the application. If a controller has multiple requests outstanding at any given time it is said to have a queue depth equal to the number of outstanding requests. When there are multiple requests outstanding a disk controller has the option of choosing the sequence in which to service them and it will attempt to optimize the order so as to achieve maximum data throughput. Requests for data blocks that reside "close" to each other on the physical drive will generally be serviced sequentially. Sophisticated algorithms increase data throughput rates by ordering pending requests optimally. Although typical user workloads demand a tiny proportion of their data at queue depths beyond four, heavily loaded database servers often see queue depths in the hundreds.

The Best.
CPUGPUSSD
Intel Core i7-6700K $330Nvidia GTX 1070 $376Samsung 850 Evo 250GB $98
Intel Core i5-6600K $220AMD RX 480 $200Samsung 850 Pro 256GB $120
Intel Core i7-4790K $339Nvidia GTX 1060-6GB $250Samsung 850 Evo 500GB $165
HDDRAMUSB
Seagate Barracuda 7200.14 1TB $45Corsair Vengeance LPX DDR4 3000 C15 2x8GB $103SanDisk Extreme 64GB $28
WD Black 6TB (2015) $270G.SKILL Trident Z DDR4 3200 C16 2x8GB $122SanDisk Extreme 32GB $21
WD Blue 1TB (2012) $50G.SKILL Trident Z DDR4 3200 C14 4x16GB $545SanDisk Extreme 16GB $16
Today's hottest deals
User Guide  •  About  •  FAQs  •  @Email  •  Privacy  •  Developer Feedback