SSD Garbage Collection Control for Battery-Saving Power Modes
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Solution Overview
Problem
Background garbage collection (BGC) in solid-state drives (SSDs) consumes a significant amount of power, which can negatively impact battery life in portable devices, especially when power is not supplied from an external source.
Innovation Solution
An information processing apparatus with a power circuit that selects between two power supply modes: one using an external power source and another using a secondary battery. The apparatus includes a second controller in the solid-state memory that executes garbage collection regardless of the host's operation mode when using external power, and determines if garbage collection is necessary when using battery power, especially during power-saving modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If background garbage collection is executed continuously to maintain SSD performance, then storage reliability is improved, but power consumption increases significantly
Solution Approach 1:
The patent applies dynamics by making the garbage collection execution state changeable based on power supply conditions. The system transitions between executing GC continuously, executing only when free space threshold is exceeded, and suspending GC entirely, allowing the storage system to adapt its behavior dynamically to available power sources and battery charge levels
Solution Approach 2:
The patent changes the operational parameters of garbage collection based on power supply mode and battery charge level. When AC power is available, GC executes continuously; when on battery power above threshold, GC executes only when free space falls below threshold; when battery charge is below threshold, GC is suspended. This parameter-based control resolves the contradiction between maintaining storage reliability and reducing power consumption
2Use of energy by moving object
If garbage collection is restricted during power-saving mode to conserve battery, then power consumption is reduced, but storage performance degrades
Solution Approach 1:
The patent applies partial action by selectively executing garbage collection only when necessary rather than continuously. When battery charge level is above the threshold, the system monitors free space and executes GC only when the free space ratio falls below a predetermined threshold, performing partial GC operations rather than continuous full GC, thus balancing power conservation with storage performance
3Reliability
If background garbage collection is executed in parallel with data operations, then storage availability is improved, but access speed degradation occurs
Solution Approach 1:
The patent applies periodic action by executing garbage collection at specific intervals rather than continuously in parallel with all data operations. The system checks power supply mode and battery charge level, then periodically evaluates whether GC should execute based on free space threshold, creating periodic GC cycles that reduce conflict with data access operations while maintaining storage availability
Data Source
AI summary
An information processing apparatus includes a power circuit, a first controller, and a solid-state memory. The solid-state memory includes a second controller and a storage medium. The power circuit supplies operating power to a constituent member, selects a first power supply mode for converting supplied power into operating power when power is supplied from an external power source, and selects a second power supply mode for converting power from a secondary battery into the operating power when AC power is not supplied from an external power source. The second controller executes garbage collection for the storage medium regardless of an operation mode notified from the first controller when the first power supply mode is selected and determines whether garbage collection for the storage medium is necessary when the second power supply mode is selected and a change to a power saving mode is instructed as the operation mode.