Processor Core Segmentation for Drive Rebuild Latency
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Solution Overview
Problem
Previous data storage systems experience decreased host I/O request processing performance during the drive rebuild time window due to the indiscriminate mixing of I/O request processing and drive rebuild jobs on the same processor cores, leading to increased latency, especially under low I/O request loads.
Innovation Solution
The technology selectively utilizes processor cores by executing drive rebuild jobs on one set of processor cores and processing host I/O requests on another set, dynamically adjusting core usage based on the number of outstanding I/O requests to maintain performance and avoid unnecessary core sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If host I/O request processing and drive rebuild jobs are processed on the same processor cores without distinction, then device complexity is reduced and resource utilization is simplified, but host I/O request processing performance deteriorates due to increased latency during drive rebuild time window
Solution Approach 1:
The patent segments processor cores into two distinct groups: a first group dedicated to drive rebuild jobs and a second group dedicated to host I/O request processing. This segmentation prevents the mixing of I/O request processing and drive rebuild jobs on individual processor cores, thereby maintaining host I/O request processing performance during the drive rebuild time window while managing complexity through organized resource allocation
Solution Approach 2:
The patent dynamically adjusts processor core assignment based on system state. Drive rebuild jobs are initially assigned to the first group of processor cores, but if I/O performance degradation is detected, the system dynamically transitions drive rebuild jobs to the second group of processor cores. This dynamic adjustment optimizes host I/O request processing performance while still allowing drive rebuild operations to proceed
2Loss of time
If processor cores are exclusively dedicated to drive rebuild jobs during the drive rebuild time window, then drive rebuild completion time is reduced through dedicated resources, but host I/O request processing capability deteriorates due to lack of available processor cores
Solution Approach 1:
The patent divides processor cores into a first group for drive rebuild jobs and a second group for host I/O request processing, ensuring both functions have dedicated resources simultaneously. This segmentation allows drive rebuild operations to utilize dedicated processor cores without interfering with host I/O processing, while the second group of processor cores maintains full host I/O processing capability throughout the drive rebuild time window
Solution Approach 2:
The patent adds a dimensional separation by creating distinct processor core groups for different functions. Instead of time-based or load-based sharing on the same cores, the system uses spatial separation (different core groups) to allow both drive rebuild and host I/O processing to occur in parallel with dedicated resources, effectively resolving the resource contention in a new dimension
Data Source
AI summary
In response to failure of a data storage drive, data previously stored on the failed drive is rebuilt on a replacement data storage drive by executing drive rebuild jobs on a first set of processor cores. While the data previously stored on the failed data storage drive is being rebuilt, a second set of processor cores is used to process host I/O (Input/Output) requests. The host I/O requests processed by the second set of processor cores may be a first set of host I/O requests processed during the data rebuild. When a current total number of outstanding host I/O requests exceeds a threshold maximum number of outstanding host I/O requests, at least one processor core in the first set of processor cores may be used to process a second set of host I/O requests while the data previously stored on the failed data storage drive is being rebuilt.