Flexible RAID Sparing via Disk Split Index Adjacency
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Solution Overview
Problem
The existing methods for scaling storage capacity in data storage systems using RAID (D+P) protection groups often result in excess storage capacity that is not utilized efficiently, especially as individual drive capacities and costs increase, due to the need to add D+P drives in increments that may not be fully utilized within a reasonable timeframe.
Innovation Solution
The implementation of a method that creates a drive subset with (D+P) plus spare sequentially indexed drives, relocating selected protection group members to spare drives to maintain split index and drive index adjacency, allowing for the creation of new protection groups without violating storage rules, and calculating adjusted spare split indices to ensure timely reconstruction or rebuilding of failed drives without excess capacity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If D+P drives are added in increments to increase storage capacity, then storage capacity is improved, but excess storage capacity is created that will not be utilized within a reasonable timeframe
Solution Approach 1:
The invention segments the drive allocation approach by introducing individual drive spares separate from the D+P protection group increments. Instead of adding drives in fixed D+P increments, the system adds one drive at a time and designates it as a spare, allowing flexible allocation of storage capacity without creating excess unused capacity.
Solution Approach 2:
The system performs preliminary action by pre-configuring drives as spares before they are needed. Each added drive is immediately designated as a spare and made available for future failures, eliminating the need to wait until a failure occurs before allocating additional storage resources. This allows the storage system to be scaled up in single drive increments while maintaining the ability to reconstruct any failed drive.
2Quantity of substance
If individual drive capacity increases due to technological advancements, then storage capacity per drive is improved, but the amount of excess storage capacity and cost increases
Solution Approach 1:
The invention changes the parameter of drive allocation from fixed D+P increments to flexible single-drive additions. By allowing the system to add drives one at a time based on actual needs rather than following rigid RAID group increments, the system can better match storage capacity to actual requirements, reducing waste from excess capacity even as individual drive prices and capacities increase.
3Adaptability or versatility
If protection group members are relocated to spare drives to enable single drive increment scaling, then storage capacity flexibility is improved, but drive manager complexity increases
Solution Approach 1:
The system uses copying by creating virtual copies of drive mappings and protection group assignments. When a drive is added as a spare, the drive manager creates virtual mappings that associate the new spare drive with existing protection groups, allowing flexible allocation without physically reconfiguring the entire storage system. This virtual copying approach simplifies the drive manager's task of managing complex drive-to-protection-group relationships.
Data Source
AI summary
In a storage system that implements RAID (D+P) protection groups a drive subset initially has (D+P) drives plus a spare drive with (D+P) splits. Spare splits are distributed with drive index and split index adjacency such that no single drive or split index contains multiple spare splits. When the drive subset is incremented by one drive a group of selected splits are relocated to the new drive based on drive index and split index adjacency such that no single drive or split index contains multiple members of a new protection group. If one of the drives is failing or fails, then an adjusted spare split index value is calculated for each protection group member on that drive so that the protection group members are rebuilt or relocated without placing more than one member of any protection group on a single drive. Adjusted spare split index values may be calculated in steps using the data split indices in ascending order and the largest drive indices in descending order.