SSD L2P Table Sharing for Thin Provisioning DRAM Efficiency
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Solution Overview
Problem
The inefficiency of logical to physical (L2P) table usage in thin provisioning systems leads to wasted resources due to unused portions of the L2P table, which are not fully utilized, especially in solid state drives (SSDs), resulting in unnecessary consumption of expensive DRAM.
Innovation Solution
The L2P table is sized to support the total memory available per client or host, with unused spaces being reallocated as temporal buffers until needed for write commands, managing these 'holes' to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the L2P table is sized to support the total memory available per client in thin provisioning systems, then the system can accommodate multiple users with virtualized storage space, but the L2P table will have unused portions resulting in wasted DRAM resources
Solution Approach 1:
The patent implements dynamic L2P table management where the table size and allocation are adjusted based on actual usage patterns. The system monitors L2P entry utilization and dynamically reallocates space from unused portions to active mappings, transforming the static L2P table into an adaptive structure that evolves with workload demands.
Solution Approach 2:
The system changes the operational parameters of the L2P table by implementing variable allocation strategies. Instead of fixed allocation, the table uses adjustable mapping densities and dynamic resizing parameters that adapt to the actual number of active L2P entries, optimizing the balance between table coverage and memory consumption.
2Adaptability or versatility
If the L2P table is made larger to support thin provisioning for multiple users, then more virtual storage space can be allocated, but the performance and power efficiency deteriorate due to managing larger table structures
Solution Approach 1:
The patent divides the large L2P table into multiple smaller segments or regions, each managed independently. This segmentation allows the system to only activate and manage the segments that are currently in use, reducing the overhead of managing the entire table structure and improving access efficiency by localizing search operations to relevant segments.
Solution Approach 2:
The system implements partial L2P table population by only creating and maintaining L2P entries for actually allocated storage regions. Instead of pre-populating the entire address space, the system dynamically creates entries as needed and maintains only the necessary portion of the table, reducing management overhead while supporting thin provisioning capabilities.
3Reliability
If the L2P table is sized to accommodate full logical address range for all users, then complete address translation coverage is achieved, but unused 'holes' in the L2P table waste expensive DRAM resources
Solution Approach 1:
The patent implements a multi-functional L2P table structure that serves dual purposes: it maintains complete address translation coverage for reliability while simultaneously functioning as a dynamically managed memory resource. The same L2P table structure is used for both address mapping and as a pool of reusable memory entries, eliminating waste by ensuring every allocated DRAM location serves a functional purpose.
Solution Approach 2:
The system implements a lifecycle management mechanism for L2P entries that includes discarding unused or stale entries and recovering their memory space for reallocation. When storage regions are deallocated or L2P mappings become obsolete, the system automatically removes these entries and returns their associated DRAM resources to the available pool, preventing permanent waste of memory capacity.
Data Source
AI summary
Logical to physical (L2P) tables are implemented in solid state drives (SSDs) to hold L2P address translations. In a thin provisioning or thin storage system, the L2P table is sized to support the total amount of memory that is available to be allocated on a per client or per host basis. During thin provisioning, the total amount of memory is not typically utilized. As such, the L2P table, which is sized to accommodate full usage of the memory allocated, is not fully utilized resulting in unused portions of the L2P table. The unused portions of the L2P table can be reallocated to use as temporal buffers until needed for write commands. Due to the reallocation, less buffers are needed.