Disk Drive Controller Command Queue Segmentation

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Solution Overview

Problem

Hard disk drives (HDDs) experience reduced performance due to a full host command queue, where incoming commands are blocked because the queue is either physically or effectively full, leading to inefficiencies in data storage and retrieval.

Innovation Solution

A storage device controller determines if the host command queue is full of pending read commands and forces the execution of one of these commands to free up space, allowing additional commands to be processed, thereby maintaining device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the host command queue is filled with pending read commands, then the host command queue appears full to the host, but the HDD can still process write commands efficiently, the host's ability to send further commands is blocked, leading to reduced device performance

Engineering Contradiction:

Improvecommand processing throughputVSAvoidhost command queue capacity

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent segments the host command queue into two separate queues: a read command queue and a write command queue. This allows write commands to be processed independently without being blocked by pending read commands, thereby maintaining overall command processing throughput while resolving the effective fullness issue

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary mechanism (the segmented queue structure with separate read and write queues) that mediates between the host's command submission and the HDD's command execution. This intermediary allows the system to maintain the appearance of a full queue to the host while actually processing commands efficiently in the background

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the host command queue is physically full, then no additional commands can be accepted, but if it is effectively full due to pending commands, the host cannot send further commands even though space may be available, reducing device performance

Engineering Contradiction:

Improvecommand queue managementVSAvoiddevice performance

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

By segmenting the command queue into read and write portions, the system simplifies queue management logic. The host can submit commands without complex visibility checks, while the controller independently manages each segment, improving both ease of operation and device performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The segmented queue structure enables self-service operation where the controller automatically manages read and write command processing independently without requiring host intervention or complex queue status checking, thereby improving both ease of operation and productivity

Inventive Principle:

Principle #25Self-service

3Reliability

If the host command queue is full of pending read commands, then write commands can still be processed efficiently, but the overall system performance is reduced due to blocked command submission

Engineering Contradiction:

Improvewrite command processingVSAvoidoverall command processing

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the command processing into independent read and write pathways. Write commands are processed reliably through the write queue without being affected by read command status, while the read queue handles read commands separately. This segmentation maintains write command reliability while improving overall command processing productivity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The segmented queue structure enables continuous processing of both read and write commands without interruption. While read commands are pending, write commands continue to be processed continuously through the separate write queue, maintaining both reliability and overall productivity

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS10678442B2Disk drive that efficiently handles random mixed-R/W command-streams

Publication Date: 2020.06.09 KK TOSHIBA

AI summary

Aspects of the present disclosure generally relate to storage devices and methods of operating the same. In one aspect, a storage device includes a disk, and a head configured to write data to and read data from the disk. The storage device also includes a controller configured to receive a read command in a host command queue, store the read command in a disk queue, and determine whether the host command queue is full of pending read commands, including the received read command. If the host command queue is full of pending read commands, the controller forces execution of one of the pending read commands.