Mapped RAID Drive Extent Pool Capacity Calculation

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Solution Overview

Problem

Traditional RAID data storage systems face limitations in adding new disks and suffer from long rebuild times due to write bandwidth bottlenecks, especially as individual disk capacities increase, leading to inefficiencies and potential data loss during rebuild processes.

Innovation Solution

The mapped RAID technology allows for the addition of individual storage drives and addresses rebuild time issues by dividing each drive into contiguous regions (drive extents), allocating spare extents across multiple drives for parallel processing, and accurately determining the effective capacity of the drive extent pool to manage storage objects effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional RAID systems use fixed stripe width configurations, then data redundancy and fault tolerance are maintained, but flexibility in adding new disks is severely limited

Engineering Contradiction:

Improveflexibility in adding new disksVSAvoidRAID configuration constraints

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the RAID storage system into multiple independent RAID groups, where each group can be configured with its own stripe width and redundancy parameters. This allows individual disks to be added to specific groups without requiring system-wide reconfiguration, enabling flexible capacity expansion while maintaining data protection through the segmented group structure.

Inventive Principle:

Principle #1Segmentation

2Reliability

If traditional RAID systems rebuild failed disks using dedicated spare disks, then data protection is maintained, but rebuild time increases significantly due to write bandwidth bottlenecks

Engineering Contradiction:

Improvedata protection during rebuildVSAvoidrebuild time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent merges multiple RAID groups into a shared pool of spare disks, allowing rebuild operations to utilize aggregate bandwidth from multiple disks simultaneously. Instead of dedicating a single spare disk to each RAID group, the system combines spare capacity across groups, enabling parallel rebuild operations that reduce total rebuild time while maintaining data protection through coordinated recovery processes.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10552078B2Determining an effective capacity of a drive extent pool generated from one or more drive groups in an array of storage drives of a data storage system that uses mapped RAID (redundant array of independent disks) technology

Publication Date: 2020.02.04 EMC IP HLDG CO LLC

AI summary

Technology for determining an effective capacity of a drive extent pool that is generated from at least one group of storage drives. A sub-group of storage drives having relatively higher physical capacities is selected from the group. The number of storage drives in the sub-group is equal to a total number of drive extents indicated by each entry in a RAID mapping table. Each storage drive in the sub-group is assigned an individual effective capacity equal to an individual physical capacity of a storage drive in the sub-group having the smallest individual physical capacity. Each storage drive in the group not contained in the sub-group is assigned an individual effective capacity equal to its own physical capacity. An effective capacity of the drive extent pool is set to a sum of the all the individual effective capacities assigned to the storage drives in the group of storage drives.