Storage Tiering Flash Wear Mitigation via Block-Level Copying
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Solution Overview
Problem
Prior approaches to automatic storage tiering accelerate wear in flash drives, leading to premature failure by copying entire slices of data, which causes excessive writing and degradation.
Innovation Solution
Accessing allocation metadata to copy data on a per-block basis, checking if each block is allocated or free before copying, thereby avoiding the transfer of unallocated blocks and reducing wear on flash storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If entire slices of data are copied during storage tiering, then data relocation is completed, but flash drive wear is accelerated and lifespan is reduced
Solution Approach 1:
The patent segments the data copying process into individual block-level operations rather than copying entire slices at once. The tiering software examines each block's allocation status and copies only allocated blocks, dividing the large-scale slice copying task into many small, selective block-level operations that reduce unnecessary writes to flash storage.
Solution Approach 2:
The patent applies partial action by copying only the necessary portion of data blocks that are actually allocated, rather than copying the entire slice. This selective copying approach performs exactly the required action (copying allocated blocks) without the excessive action of copying unallocated or free blocks, thereby reducing flash wear while maintaining data relocation effectiveness.
2Reliability
If allocation metadata is accessed and per-block copying is performed, then flash wear is reduced, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by having the tiering software access and examine allocation metadata before performing the actual data copying operation. This preliminary examination of block allocation status allows the software to identify which blocks need to be copied, preventing unnecessary writes to flash storage and extending its lifespan.
Solution Approach 2:
The patent employs self-service by having the tiering software automatically examine allocation metadata and determine which blocks are allocated and need copying. The system serves itself by using its own metadata structures to guide the copying process, eliminating the need for external control mechanisms and reducing overall system complexity despite the added per-block processing.
3Productivity
If entire slices are copied during tiering, then data relocation is achieved, but unnecessary writes to flash storage occur
Solution Approach 1:
The patent extracts only the necessary data blocks from the source slice that are actually allocated and need to be relocated. By examining allocation metadata and selectively copying only allocated blocks while leaving unallocated blocks behind, the system takes out exactly what is needed from the source location, avoiding unnecessary writes to the flash storage destination and reducing wear.
Data Source
AI summary
A technique for performing storage tiering accesses allocation metadata in a data storage system and applies that allocation metadata when relocating data from a selected extent to a target extent. The selected extent includes a range of contiguous blocks. The allocation metadata may designate each of these blocks as either allocated or free. When relocating data from the selected extent to the target extent, the technique copies data of the selected extent on a per-block basis, checking whether that block is allocated or free before copying it to the target extent.