Zone Set Manager for Shingled Magnetic Recording Disks
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Solution Overview
Problem
Shingled magnetic recording (SMR) technology increases areal density by overlapping tracks on a disk, but this reduces device reliability due to the absence of guard spaces, making storage systems more prone to errors and failures.
Innovation Solution
A storage system that creates a zone set by arbitrarily selecting disks for membership, using a random number generator to distribute data across multiple zones on different disks, ensuring data durability and access efficiency while minimizing the impact of disk failures, and using weights or eligibility criteria to influence disk selection based on health and activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If shingled magnetic recording (SMR) technology is used to increase areal density by overlapping tracks, then storage capacity is improved, but device reliability deteriorates due to the absence of guard spaces between tracks
Solution Approach 1:
The patent segments the storage system into multiple independent disks organized in zone sets, where each zone set contains zones from different disks. This segmentation isolates failures to individual disks while maintaining overall system reliability, directly addressing the reliability deterioration caused by SMR technology's overlapping tracks without guard spaces.
Solution Approach 2:
The patent changes the organizational parameter from traditional RAID disk groups to zone sets that arbitrarily select zones across multiple disks. This parameter change in data distribution strategy enhances reliability by ensuring that SMR disk failures do not catastrophically impact the entire storage system, while preserving the high areal density benefits of SMR technology.
2Device complexity
If data is clustered onto fewer disks in a RAID array, then device complexity is reduced, but the impact of disk failures on the storage system increases
Solution Approach 1:
The patent segments data across multiple zone sets distributed on different disks, rather than clustering on fewer disks. This segmentation reduces the impact of any single disk failure while maintaining manageable system complexity through the zone set manager that tracks zone memberships and handles failover automatically.
Solution Approach 2:
The patent introduces a new organizational dimension by creating zone sets that span across multiple disks arbitrarily, rather than using traditional RAID striping patterns. This dimensional change in data organization allows the system to distribute data more effectively across the storage infrastructure, reducing failure impact while maintaining complexity at acceptable levels through automated management.
3Manufacturing precision
If zones are written sequentially on SMR disks, then manufacturing precision requirements are reduced, but access efficiency deteriorates due to sequential write constraints
Solution Approach 1:
The patent segments I/O operations across multiple zone sets on different disks, allowing parallel access to multiple zones simultaneously. This segmentation mitigates the sequential write constraint of individual SMR disks by distributing I/O workload across multiple independent zones, thereby maintaining access efficiency while preserving the manufacturing simplicity of SMR technology.
Solution Approach 2:
The patent merges multiple zones from different SMR disks into zone sets that function as a unified storage resource. By combining zones across multiple disks with different sequential write states, the system achieves improved access efficiency through parallel operations while maintaining the manufacturing precision advantages of SMR technology on each individual disk.
Data Source
AI summary
A storage system writes an object across zones of a set of zones (“zone set”). Each zone of a zone set is contributed from an independently accessible storage medium. To create a zone set, the storage system arbitrarily selects disks to contribute a zone for membership in the zone set. This results in a fairly even distribution of zone sets throughout the storage system, which increases fault tolerance of the storage system. Although disk selection for zone set membership is arbitrary, the arbitrary selection can be from a pool of disks that satisfy one or more criteria (e.g., health or activity based criteria). In addition, weights can be assigned to disks to influence the arbitrary selection. Although manipulating the arbitrary selection with weights or by reducing the pool of disks reduces the arbitrariness, this evenly distributes zone sets while accounting for client demand and/or disk health.