Host-Assisted IO Service Levels via False-Positive Signaling
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Solution Overview
Problem
Storage systems face issues with excessive queuing of IO operations, leading to misleading response time measurements and frequent queue-full conditions, which adversely impact host device performance due to varying workloads and burst operations.
Innovation Solution
Implementing host-assisted IO service levels using false-positive signaling, where the storage system communicates with host devices to adjust queuing behavior, specifically by generating false-positive signals to throttle IO operations for logical storage devices with lower SLOs, thereby prioritizing higher SLO devices and avoiding excessive queuing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the storage system processes all IO operations from multiple host devices with varying workloads, then the storage system can serve all hosts, but IO bursts from one or more hosts can overwhelm the limited IO queues and resources, leading to excessive queuing and misleading response time measurements
Solution Approach 1:
The patent segments IO operations into different priority queues based on SLO classifications. High-priority SLO devices receive dedicated queue access while low-priority SLO devices are throttled during resource contention, preventing IO bursts from overwhelming the entire system and maintaining accurate response time measurements for critical devices.
Solution Approach 2:
The patent applies different service quality levels to different logical storage devices based on their SLO classifications. High-priority devices receive preferential treatment with guaranteed queue access and lower latency, while low-priority devices accept reduced service during peak loads, allowing the system to maintain measurement precision for critical operations.
2Device complexity
If the storage system allocates limited IO queues to individual host devices, then queue management is simplified, but IO bursts can still overwhelm these limited queues causing excessive queuing and frequent queue-full conditions that adversely impact host device performance
Solution Approach 1:
The patent implements dynamic queue allocation where the storage system adjusts queue access rights in real-time based on current load conditions and SLO priorities. During normal operation, multiple hosts share queues efficiently; during IO bursts, the system dynamically throttles low-priority hosts to prevent queue overflow, maintaining host device performance without requiring complex static queue management.
Solution Approach 2:
The patent employs feedback mechanisms where the storage system monitors queue depth and IO patterns, then adjusts throttling levels for low-priority SLO devices accordingly. This closed-loop control prevents queue-full conditions by proactively limiting throughput when queues approach capacity, thereby maintaining host device productivity while keeping queue management relatively simple.
3Reliability
If the storage system signals queue-full conditions frequently to host devices to manage load, then queue management is improved, but this excessive signaling adversely impacts the performance of the host devices
Solution Approach 1:
The patent applies preliminary throttling to low-priority SLO devices before their IO operations would cause queue-full conditions. By proactively limiting throughput based on predicted load and SLO priority, the system prevents queue overflow scenarios, eliminating the need for frequent queue-full signaling and maintaining host device performance while ensuring reliable queue management.
Data Source
AI summary
An apparatus comprises at least one processing device. The at least one processing device is configured to identify at least one logical storage device that has a first service level objective and is exhibiting a deficiency in one or more performance metrics, to identify one or more additional logical storage devices each having a second service level objective lower than the first service level objective and not exhibiting a deficiency in the one or more performance metrics, to generate at least one false-positive signal specifying the one or more additional logical storage devices as each exhibiting a deficiency in the one or more performance metrics, and to provide the at least one false-positive signal to at least one host device. The at least one host device is configured to respond to the at least one false-positive signal by throttling input-output operations for the one or more additional logical storage devices.