Storage Aggregate Shrinking by Data Relocation and Disk Replacement
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Solution Overview
Problem
Current storage appliances do not support reducing the provisioned storage capacity of a disk or aggregate, leading to wasted space, despite mechanisms for dynamically increasing capacity being available.
Innovation Solution
The method involves identifying a shrink region within the aggregate, relocating valid data from this region to other disks, and either removing the disk or adding a smaller disk with mirrored data to reduce capacity, leveraging existing data mirroring technology and file system block reallocator functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage capacity is dynamically increased by adding disks to the aggregate, then the provisioned storage capacity is improved, but the device complexity increases
Solution Approach 1:
The patent implements dynamic adjustment of storage capacity by allowing the aggregate to grow when capacity is reached and shrink when capacity is reduced. The system can dynamically add or remove disks from the aggregate based on storage needs, making the storage structure flexible and adaptable rather than static.
Solution Approach 2:
The storage system is divided into discrete disk units that can be independently added to or removed from the aggregate. Each disk is a separate component that can be managed individually, allowing flexible configuration of the total storage capacity by combining or removing specific disk units.
2Quantity of substance
If storage capacity is reduced by removing disks from the aggregate, then storage utilization is improved, but system availability deteriorates due to potential downtime
Solution Approach 1:
Before removing a disk from the aggregate, the system performs preliminary actions by first relocating all valid data from the disk to other disks in the aggregate. This data relocation is completed before the actual disk removal, ensuring that no data is lost and the system remains operational throughout the process.
Solution Approach 2:
The system uses an intermediary mechanism (data relocation process) between the disk removal action and the final state. By introducing the data relocation step as an intermediary process, the system can safely remove disks without immediately impacting data accessibility, thus maintaining availability during the transition.
3Device complexity
If data is relocated from the shrink region to other disks, then the shrink region can be removed, but the operation time increases
Solution Approach 1:
The data relocation process continues until all valid data from the shrink region has been successfully moved to other disks. The system maintains continuous operation during this process, ensuring that data relocation is completed thoroughly before the disk is removed, which prevents data loss but extends the operation time.
Data Source
AI summary
Systems and methods for reducing the provisioned storage capacity of a storage device or aggregate of storage devices are provided. According to one embodiment, the size of the aggregate may be reduced by shrinking the file system of the storage appliance and removing a selected storage device from the aggregate. When an identified shrink region is less than the entire addressable space of the selected storage device, the file system is shrunk by relocating data from the shrink region of the selected storage device to one or more regions outside of the shrink region, mirroring data of the selected storage device from outside of the shrink region to a smaller storage device added to the aggregate, and then removing the selected storage device after the mirrors are in sync, thereby reducing the provisioned storage capacity by the difference in size between the selected storage device and the smaller storage device.