Spare Super Block Segmentation for Power-Failure Write Recovery
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Solution Overview
Problem
Storage devices face performance degradation due to host write command timeouts when power failures occur, leading to critical reclaim states that deplete the spare block pool and hinder normal operations.
Innovation Solution
The storage device manages free super blocks by dividing them into sub-super blocks when the pool is at a critical level, allowing continued operation by allocating sub-super blocks for host writes and reducing the need for full super block closures during power failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the storage device enters a critical reclaim state to prevent writing to super blocks opened prior to power failure, then data integrity is improved, but host write command performance deteriorates due to timeouts
Solution Approach 1:
The patent divides a super block into multiple segments (first super block portion and second super block portion) when the number of free super blocks falls below a threshold. This segmentation allows the storage device to allocate segments individually for host write commands rather than treating the entire super block as unavailable, thereby maintaining data integrity while preserving host write performance during low free super block conditions
2Productivity
If the storage device allocates super blocks for host writes when operating close to the critical threshold, then host write performance is improved, but the risk of data integrity issues increases during successive power failures
Solution Approach 1:
The patent implements a preliminary action by monitoring the number of free super blocks and detecting when it falls below a threshold before power failures occur. Upon detecting this condition, the storage device proactively segments available super blocks into allocatable portions, preparing the system in advance to handle host write commands safely even when operating close to critical thresholds, thereby preventing data integrity issues during successive power failures
3Productivity
If the storage device divides a super block into sub-super blocks, then the number of allocatable units for host writes increases, but the device complexity increases
Solution Approach 1:
The patent applies dynamics by making the super block structure adaptive rather than static. Super blocks are segmented into sub-super blocks dynamically based on the number of free super blocks available. When free super blocks are sufficient, entire super blocks remain intact; when they fall below the threshold, segmentation occurs automatically. This dynamic approach increases allocatable units for host writes while managing complexity through conditional, rather than permanent, structural changes
Data Source
AI summary
A storage device may manage free super blocks when a number of empty super blocks is at a critical level. The storage device includes a memory including multiple dies divided into physical blocks. A controller on the storage device may form super blocks from the physical blocks. The controller may store information for empty super blocks in a free pool. When the storage device is initialized and the controller receives a host write request, the controller may determine that a number of empty super blocks in the free pool is less than a warning threshold. The controller may obtain a first super block from the free pool, divide the first super block into a set of sub-super blocks, and allocate one of the sub-super blocks for the host write request, enabling the device to handle more power/program failures when the device is at or close to a critical threshold.