Hybrid HDD Metadata Storage in Volatile Memory and NAND Flash
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Solution Overview
Problem
Current hard disk drives (HDDs) face challenges in balancing storage capacity and access latency, leading to a narrow range for input/output operations per second (IOPS), while solid state drives (SSDs) face complications in high-throughput interfaces and flash translation layers, resulting in performance gaps and constraints in overall storage systems.
Innovation Solution
A system that integrates NAND dies into HDDs to store metadata, using a modified HDD controller to interface with both HDD storage media and NAND flash memory, isolating metadata from data and optimizing IOPS by managing metadata in volatile memory and synchronizing it with NAND dies, thus reducing metadata access latency and enhancing IOPS capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metadata and data are stored in different locations in an HDD, then data storage capacity is improved, but metadata access latency increases due to multiple head movements
Solution Approach 1:
The patent segments the storage system into two distinct parts: metadata storage (in volatile memory and NAND flash) and data storage (in HDD platters). This segmentation allows metadata to be accessed independently from data, eliminating the need for head movements when accessing metadata and thereby reducing metadata access latency while maintaining high storage capacity for data.
Solution Approach 2:
The patent introduces volatile memory and NAND flash as intermediary storage layers between the host and the HDD platters. These intermediaries cache and manage metadata, allowing fast access without requiring physical head movements to the data storage locations on the platters, thus resolving the contradiction between storage capacity and metadata access latency.
2Device complexity
If a single HDD is used to store both metadata and data, then device complexity is reduced, but IOPS performance is limited due to the narrow range for IOPS of a single HDD
Solution Approach 1:
The patent merges multiple storage technologies (HDD platters for data, NAND flash for metadata persistence, and volatile memory for metadata caching) into a unified storage system. This hybrid architecture combines the high capacity of HDDs with the high-speed access of SSD components, achieving high IOPS performance while maintaining a relatively simple unified device interface to the host.
Solution Approach 2:
The storage system is designed with multi-functionality: the same controller manages both metadata operations (in volatile memory and NAND) and data operations (on platters), and the system can handle both sequential and random access patterns efficiently. This universal design allows a single device to deliver high IOPS across different workloads without requiring multiple separate devices.
3Speed
If metadata is stored in volatile memory only, then metadata access speed is improved, but data reliability decreases due to loss of metadata on power failure
Solution Approach 1:
The patent implements preliminary action by continuously caching metadata in volatile memory for fast access while simultaneously maintaining synchronized copies in NAND flash storage. Before any power failure can occur, the system has already persisted the metadata to non-volatile storage, ensuring that when power is restored, the metadata can be recovered from NAND without data loss, thus maintaining both speed and reliability.
Solution Approach 2:
The system provides beforehand cushioning against power failures by using NAND flash as a protective layer. The volatile memory is protected by the presence of NAND flash, which acts as a safety cushion that preserves metadata even when power is lost. This dual-layer approach ensures that the speed benefits of volatile memory are maintained while the reliability risks are mitigated by the non-volatile NAND storage.
Data Source
AI summary
One embodiment provides a system which facilitates operation of a storage system. During operation, the system receives, by a storage engine, a request to write data to a hard disk drive. The system determines metadata associated with the data. The system stores the metadata in a volatile memory associated with the storage engine. The system identifies a physical address in a first non-volatile solid-state memory to which to write the metadata, wherein the first non-volatile solid-state memory is accessible via a controller of the hard disk drive. The system writes the metadata to the first non-volatile solid-state memory based on the physical address. The system writes the data to the hard disk drive.