Storage Garbage Collection Segmentation for SSD Lifetime
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Solution Overview
Problem
In storage systems, writing data often requires migrating half a block of data, leading to significant latency and reduced performance due to the need for frequent garbage collection to reclaim memory from unused data.
Innovation Solution
Implementing a modified garbage collection method that separates data into short-lived and long-lived blocks, where short-lived data is written to one block and migrated to a distinct long-lived block only if determined to be live, reducing unnecessary migrations and write amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written to persistent storage using traditional garbage collection, then memory can be reclaimed from unused data, but significant latency is introduced and system performance is reduced due to frequent data migration
Solution Approach 1:
The patent segments data into two distinct categories: short-lived data and long-lived data. Short-lived data is stored in short-lived blocks while long-lived data is stored in long-lived blocks. This segmentation allows the garbage collector to focus only on short-lived blocks, eliminating the need to migrate long-lived data and thereby reducing migration overhead while maintaining effective memory reclamation.
Solution Approach 2:
The patent extracts long-lived data from the garbage collection process by identifying and isolating it in separate long-lived blocks. The garbage collector is modified to exclude long-lived blocks from its operation, effectively removing the harmful migration of long-lived data while preserving the ability to reclaim memory from short-lived data that is no longer in use.
2Reliability
If traditional garbage collection migrates all live data, then unused data can be reclaimed, but the number of program/erase cycles increases reducing the lifetime of solid-state memory modules
Solution Approach 1:
By segmenting storage blocks into short-lived and long-lived categories, the patent ensures that program/erase cycles are only applied to short-lived blocks during garbage collection. Long-lived blocks are excluded from migration operations, thereby reducing the total number of program/erase cycles and extending the operational lifetime of solid-state memory modules while maintaining effective memory reclamation from obsolete short-lived data.
Solution Approach 2:
The patent applies the principle of discarding and recovering by selectively reclaiming only short-lived data that is no longer in use, while preserving long-lived data in dedicated blocks. This selective recovery process minimizes unnecessary program/erase cycles on long-lived data, thereby extending module lifetime while still achieving effective memory reclamation where needed.
3Productivity
If data is separated into short-lived and long-lived blocks, then unnecessary data migration is reduced, but the complexity of the garbage collection operation increases
Solution Approach 1:
While segmentation into short-lived and long-lived blocks does increase structural complexity, it simplifies the garbage collection operation itself by providing clear boundaries and identification mechanisms. The garbage collector can use metadata or block identifiers to quickly determine which blocks are short-lived and require collection, eliminating the need for complex analysis of data longevity and thereby improving overall data migration efficiency.
Data Source
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Figure 2E
AI summary
A method for managing data. The method includes receiving (302) a first request to write data to persistent storage and in response to the first request, writing (312) the data to a short-lived block in the persistent storage, where the data is short-lived data or data of unknown longevity. The method further includes performing a modified garbage collection operation that includes: selecting a first frag page in a first block, determining that the first frag page is live, and migrating, based on the determination that the first frag page is live, the first frag page to a long-lived block in the persistent storage, where the long-lived block is distinct from the short-lived block and wherein the long-lived block does not include any short-lived data.