SMR File System Storage Allocation for Density and Performance
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Solution Overview
Problem
Existing data storage systems face inefficiencies in managing data on tiered storage volumes that combine shingled magnetic recording (SMR) and conventional magnetic recording (CMR) or solid-state drives, particularly in optimizing storage density and performance without compromising CPU usage or file system efficiency.
Innovation Solution
A file system that allocates space based on data type, using a unified controller to manage SMR and CMR/SDD tiers by maintaining separate allocation for file data and metadata, employing deferred allocation and compaction techniques to optimize storage density and reduce fragmentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SMR disk is used to maximize storage density, then storage capacity is improved, but random write performance deteriorates
Solution Approach 1:
The storage system is segmented into two distinct parts: an SMR disk for sequential write operations (file data) and a randomly-writable data store (CMR disk or SSD) for random write operations (metadata). This segmentation allows each component to operate in its optimal performance mode, resolving the contradiction between storage density and random write performance.
Solution Approach 2:
Different quality characteristics are assigned to different parts of the storage system. The SMR disk is optimized for sequential access and high storage density, while the CMR/SSD portion is optimized for random access and fast writes. This local quality differentiation allows the system to achieve both high storage capacity and good random write performance simultaneously.
2Quantity of substance
If metadata is stored on SMR disk, then storage capacity is improved, but file system performance deteriorates
Solution Approach 1:
The storage system is segmented into two distinct parts: an SMR disk for sequential write operations (file data) and a randomly-writable data store (CMR disk or SSD) for random write operations (metadata). This segmentation allows each component to operate in its optimal performance mode, resolving the contradiction between storage density and random write performance.
3Productivity
If separate allocation for file data and metadata is implemented, then storage efficiency is improved, but device complexity increases
Solution Approach 1:
A firewall mechanism is introduced as an intermediary between the file system and the two-tier storage system. This firewall automatically routes file data to the SMR disk and metadata to the CMR/SSD, managing the separate allocation without requiring complex file system logic. The firewall handles the complexity of differentiated storage management while maintaining simple interfaces for applications.
Data Source
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AI summary
A file system executing on a computing system is configured to efficiently manage and store data on a tiered storage volume using hybrid media that includes a shingled magnetic recording (SMR) data store, such as an SMR disk drive, and a randomly-writable data store, such as a conventional magnetic recording (CMR) disk or solid-state drive (SSD) using flash memory. Write operations in the SMR disk are performed in a sequential manner to optimize storage density on the disk. The file system utilizes logic incorporated in an allocator that monitors I/O operations on the computing system - for example, write requests from applications executing on the system - to determine if a request is associated with file data or metadata. If the request is for metadata, then the allocator allocates space on the SSD/CMR for the metadata, and if the request is for file data, then space is allocated on the SMR disk.