Indirection Data Structures for SMR Metadata Management
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Solution Overview
Problem
As storage densities increase in shingled magnetic recording (SMR) drives, managing file system metadata becomes challenging due to limited space in perpendicular magnetic recording (PMR) zones, which are typically used for metadata storage alongside user data in SMR zones.
Innovation Solution
A storage control system is implemented to redirect a subset of metadata from PMR zones to SMR zones when a usage condition is met, using an indirection data structure to correlate metadata locations, allowing for efficient storage and retrieval of metadata across both zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metadata is stored in PMR zones alongside user data in SMR zones, then metadata storage is simplified, but storage capacity for user data is reduced due to limited PMR zone space
Solution Approach 1:
The patent segments metadata storage into two distinct locations: PMR zones for critical metadata and SMR zones for non-critical metadata. This segmentation allows the system to maintain simplicity in metadata management while significantly increasing user data storage capacity by utilizing both zones appropriately.
Solution Approach 2:
The patent introduces an indirection data structure as an intermediary mechanism that maps logical metadata addresses to physical locations in either PMR or SMR zones. This intermediary layer transparently handles the complexity of distributed metadata storage, maintaining ease of access while enabling efficient utilization of storage capacity across both zones.
2Reliability
If all metadata is stored in PMR zones, then metadata access is fast and reliable, but storage flexibility and capacity are limited
Solution Approach 1:
The patent applies local quality by storing different types of metadata in different zones based on their access characteristics. Critical metadata that requires frequent access and high reliability is stored in PMR zones, while non-critical metadata with lower access requirements is stored in SMR zones. This differentiated approach optimizes both reliability and storage flexibility.
Solution Approach 2:
The patent implements dynamic metadata management where the storage location of metadata can change over time based on usage patterns. The system monitors metadata access frequency and automatically migrates metadata between PMR and SMR zones, allowing the storage system to adapt to changing requirements and optimize performance dynamically.
3Productivity
If SMR zones are used for user data only, then data writing efficiency is high, but metadata management becomes constrained by PMR zone limitations
Solution Approach 1:
The patent makes SMR zones multi-functional by enabling them to store both user data and non-critical metadata. This universal usage of SMR zones eliminates the constraint of PMR zone limitations for metadata management while preserving the high writing efficiency of SMR zones for user data, as the system can independently manage metadata in designated SMR regions without interfering with user data write operations.
Data Source
AI summary
Described herein are systems, methods, and software to manage metadata in a data storage device. In one example, a data storage device includes a first storage zone, a shingled magnetic recording (SMR) zone, and a storage control system. The storage control system is configured to maintain metadata in a metadata location of the first storage zone for user data in the SMR zone. The storage control system is further configured to, responsive to a usage condition being satisfied for the metadata in the metadata location, identify metadata locations in the SMR zone to redirect and store the metadata. The storage control system is also configured to maintain an indirection data structure in the metadata location of the first zone that correlates the metadata locations in the SMR zone to the metadata.