Flash Memory Storage Controller Dynamic Wear Allocation

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Solution Overview

Problem

Storage systems with flash memories face a challenge in maintaining a balance between the lifetime and logical storage capacity due to the upper limit on rewrites, leading to inefficient use of storage capacity when data has a low rewrite frequency.

Innovation Solution

A storage system that dynamically allocates vacant physical storage areas to logical storage areas based on rewrite frequency, allowing for flexible adjustment of available and surplus capacities to extend the lifetime of flash memory packages while maintaining logical storage capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a write area is secured in advance in a storage apparatus used for storing data with low rewrite frequency, then the lifetime of the storage medium is maintained, but the logical storage capacity decreases

Engineering Contradiction:

Improvelifetime of storage mediumVSAvoidlogical storage capacity

Core Design Contradiction:

Duration of action of stationary objectVSQuantity of substance

Solution Approach 1:

The patent implements dynamic allocation of physical storage areas to logical storage areas based on actual rewrite frequency monitoring. The medium controller continuously monitors rewrite frequencies and adjusts the allocation of physical storage areas dynamically, transforming the static write area allocation into a dynamic system that adapts to actual usage patterns. This resolves the contradiction by allowing the system to maintain lifetime protection only when actually needed while maximizing storage capacity during low-rewrite periods.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the allocation parameter (ratio of physical to logical storage areas) based on monitored rewrite frequency. When rewrite frequency exceeds a threshold, the system adjusts the allocation to reserve additional physical storage areas; when rewrite frequency is low, it reduces the reserved area to maximize usable capacity. This parameter adjustment mechanism resolves the contradiction between lifetime protection and storage capacity utilization.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of stationary object

If the number of rewrites of a flash memory reaches its upper limit, then the lifetime is exhausted, but the ability to write new data is lost

Engineering Contradiction:

Improvelifetime of flash memoryVSAvoidability to write new data

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent segments the physical storage areas into multiple zones and allocates them to different logical storage areas. By dividing the storage medium into segments and monitoring rewrite frequencies per logical area, the system can selectively manage wear across different segments. This allows the system to extend overall lifetime by redistributing write operations across available segments while maintaining data write capability through proper segment management.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The medium controller acts as an intermediary between the host computer and the flash memory packages. It monitors rewrite frequencies, manages the allocation of physical storage areas to logical storage areas, and controls write operations to prevent any single physical area from reaching its rewrite limit. This intermediary layer protects the flash memory from excessive writes while ensuring data can always be written by redirecting to available physical areas.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If data is written frequently to a storage medium with upper limit rewrites, then the logical storage capacity is充分利用, but the lifetime decreases

Engineering Contradiction:

Improvedata write frequencyVSAvoidlifetime of storage medium

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The system implements a feedback mechanism where the medium controller continuously monitors the rewrite frequency of each logical storage area and uses this information to adjust the allocation of physical storage areas. When rewrite frequency increases, the system receives feedback and responds by allocating additional physical storage areas to that logical area, thereby distributing wear and extending the overall lifetime while maintaining high data write productivity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9817768B2Storage system and data storing method

Publication Date: 2017.11.14 HITACHI VANTARA LTD

AI summary

Provided is a storage system including: a storage medium including a plurality of physical storage areas having an upper limit number of rewrites, and a medium controller that controls I/O (input/output) of data to/from the plurality of physical storage areas; and a storage controller connected to the storage medium, wherein when any of the physical storage areas is not allocated to a write destination logical storage area among a plurality of logical storage areas, the medium controller allocates a vacant physical storage area among the plurality of physical storage areas to the write destination logical storage area and writes write target data to the allocated vacant physical storage area, and the plurality of logical storage areas includes an available logical area group determined based on a relationship between an available capacity of a logical storage capacity and a rewrite frequency of the plurality of physical storage areas.