Two-Level Hash Table Management for SSD Lifespan
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Solution Overview
Problem
As data storage capacity increases, managing hash tables becomes challenging due to limited memory capacity, leading to inefficiencies in storage and access speed, especially when dealing with large datasets like 200 TB of data, which requires excessive memory space for hash entries.
Innovation Solution
Implementing a two-level hash table storage structure, where a high-speed storage device (e.g., memory) manages the first-level hash table and a solid-state drive (SSD) handles the second-level hash table, allowing for efficient merging of entries when the first-level table is full, transforming random writes into continuous operations and prolonging SSD service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a hash table is managed in memory to enable quick determination of whether data is redundant, then access speed is improved, but the scale of the hash table is limited by memory capacity
Solution Approach 1:
The patent divides the hash table into two segments: a first hash table stored in memory for quick access and a second hash table stored in rear-end storage for large-scale data. This segmentation allows the system to maintain fast access speeds for frequently accessed data while accommodating large volumes of data in the rear-end storage, thereby resolving the contradiction between access speed and hash table scale.
2Quantity of substance
If the first hash table is full and needs to store more hash values, then storage capacity is improved, but I/O operations increase due to merging requirements
Solution Approach 1:
The patent pre-allocates a third hash table in the first storage device before the first hash table becomes full. When the first hash table is full, the system can immediately switch to the pre-allocated third hash table without requiring immediate merging operations. This preliminary action reduces the frequency and impact of I/O operations, thereby improving productivity while maintaining storage capacity.
3Quantity of substance
If hash values are merged from the first hash table to the second hash table, then storage capacity is improved, but access speed deteriorates due to slower rear-end storage
Solution Approach 1:
The patent applies local quality by keeping the most frequently accessed hash values in the first hash table in memory, while storing less frequently accessed hash values in the second hash table in rear-end storage. This differentiation allows the system to maintain fast access speeds for hot data while providing large storage capacity for cold data, thereby resolving the contradiction between storage capacity and access speed.
Data Source
AI summary
Techniques manage a hash table, and a computer program product. The techniques involve: in response to receiving a write request, determining whether a first hash value associated with the write request is stored in a Haidian District set of hash tables, the set of hash tables including at least a first hash table and a second hash table, the first hash table being a currently valid hash table for the first storage device, the second hash table being stored in a second storage device, an access speed of the first storage device being faster than that of the second storage device; in response to determining that the first hash value is not stored in the set of hash tables and the first hash table is full, setting a pre-allocated third hash table in the first storage device as the currently valid hash table in the first storage device; writing a first entry into the third hash table, the first entry including the first hash value; and merging entries in the first hash table with entries in the second hash table for storage into the second storage device. With such techniques, a two-level hash table structure is built, and the hash table management efficiency is improved.