Mapped RAID Shared Hot Spare Pool for Disk Group Rebuilds
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Solution Overview
Problem
Conventional storage systems with mapped RAID configurations face challenges in efficiently managing hot spare extents, leading to potential data unavailability and loss due to isolated hot spare extents that cannot be shared across disk groups, resulting in increased risk of Double Faulted RAID Group conditions and data unavailability during rebuild processes.
Innovation Solution
Implementing a shared pool of hot spare extents across multiple disk groups, allowing hot spare extents to be shared and utilized across disk groups for rebuilding, thereby reducing the risk of data unavailability and loss by increasing available capacity without adding physical disks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot spare extents are isolated within each disk group, then each disk group has dedicated hot spare capacity, but the overall storage system has insufficient hot spare capacity to handle multiple simultaneous failures and rebuild performance is limited
Solution Approach 1:
The patent merges hot spare extents from multiple disk groups into a unified shared pool. Instead of isolating hot spares within individual disk groups, the system combines them across disk group boundaries, allowing any disk group to utilize hot spare capacity from any other disk group when failures occur. This resolving the contradiction by pooling resources to achieve both sufficient capacity and high reliability.
Solution Approach 2:
The shared hot spare pool creates a universal resource that serves multiple disk groups simultaneously. The hot spare extents are no longer dedicated to single disk groups but become multi-functional resources that can be dynamically allocated to any disk group experiencing failures, thereby increasing overall system reliability without requiring additional physical disks.
2Productivity
If dedicated hot spare disks are allocated to each disk group, then rebuild operations can proceed in parallel, but storage provisioning efficiency decreases and physical disk requirements increase
Solution Approach 1:
The patent combines hot spare resources from multiple disk groups into a shared pool, eliminating the need for separate dedicated hot spare disks in each disk group. This reduces device complexity and disk configuration overhead while maintaining the ability to perform parallel rebuild operations across multiple disk groups simultaneously using the pooled resources.
Solution Approach 2:
The shared hot spare pool enables disk groups to self-service their rebuild needs dynamically. When a disk fails, the affected disk group automatically draws hot spare capacity from the shared pool without requiring manual allocation or dedicated reserves, thereby simplifying management while preserving rebuild performance.
3Ease of operation
If hot spare extents are confined to individual disk groups, then management is simplified, but the risk of Double Faulted RAID Group conditions increases and data unavailability risk rises during rebuild processes
Solution Approach 1:
The system implements monitoring and management of the shared hot spare pool with feedback mechanisms that track capacity utilization across disk groups. When hot spare capacity is consumed in one disk group, the system dynamically adjusts allocation from the shared pool, providing feedback-driven resource management that maintains data availability while simplifying overall hot spare management through centralized control.
Solution Approach 2:
The shared hot spare pool creates a universal resource that serves multiple disk groups, reducing the risk of Double Faulted RAID Group conditions. When one disk group experiences failures, it can draw capacity from the shared pool rather than being limited to its own isolated hot spares, thereby maintaining data availability while the centralized management simplifies operations.
Data Source
AI summary
An apparatus comprises a processing device configured to maintain, for a storage system implementing a mapped redundant array of independent disks (RAID) configuration including disk groups providing RAID groups comprising data and hot spare extents, a shared pool of hot spare extents comprising first and second sets of hot spare extents from first and second ones of the disk groups. The processing device is further configured to detect failure of a disk in the first disk group, to determine whether available ones of the first set of hot spare extents provide sufficient storage capacity for rebuilding the failed disk and, responsive to determining that available ones of the first set of hot spare extents do not provide sufficient storage capacity for rebuilding the failed disk, to rebuild the failed disk utilizing one or more of the second set of hot spare extents in the shared pool of hot spare extents.