RAID Extent Allocation for System Disk Bottleneck Resolution
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Solution Overview
Problem
The unbalanced processing capability between system disks and user disks in mapped RAID systems leads to a system bottleneck, reducing the overall performance due to fewer credits available for user IO processing on system disks.
Innovation Solution
A method that determines spare extents associated with system disks and their adjacent relationships within a RAID stripe to optimize the distribution of disk extents, reducing the number of RAID stripes affected by system disk performance and improving overall system performance by utilizing spare extents more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If system disks are used to build RAID stripes, then the capacity utilization of system disks is improved, but the user IO processing speed deteriorates due to fewer credits available for user IO
Solution Approach 1:
The patent segments the RAID stripe construction process by identifying and separating system disk extents from user disk extents. It analyzes the adjacent relationship of used extents on system disks and selectively avoids placing additional system disk extents in the same stripe when alternatives exist. This segmentation allows the system to optimize for either capacity utilization or IO speed depending on the configuration, resolving the contradiction between using system disk capacity and maintaining user IO performance.
2Quantity of substance
If spare extents on system disks are utilized, then the overall system capacity is improved, but the system bottleneck worsens due to unbalanced processing capability
Solution Approach 1:
The patent implements a dynamic extent selection mechanism that adapts to the current state of RAID stripe construction. By analyzing the adjacent relationship of already-used extents on system disks, the system dynamically decides whether to continue using system disk extents or switch to user disk extents for the current stripe. This dynamic approach prevents system disk bottlenecks while maximizing capacity utilization across the RAID array.
Solution Approach 2:
The patent employs feedback by continuously monitoring the composition of RAID stripes and the usage status of system disk extents. The adjacent relationship analysis provides feedback about the current stripe's extent distribution, which informs subsequent decisions about extent selection. This feedback loop ensures that system disk extents are utilized efficiently without creating performance bottlenecks, balancing capacity and throughput.
Data Source
AI summary
Techniques manage redundant arrays of independent drives (RAID). The techniques involve: in response to a target stripe to be built in the RAID, determining, from a resource pool, whether there are spare extents associated with at least one system disk. The techniques further involve: in response to determining that there are spare extents associated with at least one system disk, determining an adjacent relationship of used extents associated with the at least one system disk within a RAID stripe. The techniques further involve: determining, based on the adjacent relationship and the spare extents, an extent for building the target stripe. Accordingly, the total number of the RAID stripes including extents associated with the system disks can be reduced significantly, and a balance can be achieved within spare extents associated with system disks and spare extents associated with user disks for building a RAID stripe.