Disk Slice Reconstruction Priority Management

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Solution Overview

Problem

In storage systems, when a solid-state disk malfunctions, the available spare disk slices can only restore one malfunctioning disk slice, leading to potential data loss if another disk fails, as there are no idle slices left for reconstruction, especially if metadata storage units go offline, affecting user data accessibility.

Innovation Solution

A method that determines the priority of storage units and selects replacing disk slices from available units with performance levels not lower than a threshold, ensuring higher priority units are reconstructed first, thereby reducing data loss and maintaining system performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If idle disk slices are used to restore malfunctioning disk slices in the slice pool, then the malfunctioning disk slices can be reconstructed, but once the idle disk slices are exhausted, no further reconstruction can occur leading to potential data loss

Engineering Contradiction:

Improvedisk slice reconstruction capabilityVSAvoidavailable idle disk slices

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system dynamically adjusts the reconstruction strategy by introducing priority levels for different storage units. Instead of treating all reconstruction operations equally, the system dynamically selects which storage units to reconstruct first based on their priority (metadata storage units have higher priority than user data storage units). This dynamic approach ensures that critical metadata remains accessible while managing limited idle disk slices efficiently.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of reconstruction priority by introducing a priority classification system. Storage units are assigned different priority levels based on their importance (metadata vs. user data). This parameter change allows the system to preferentially allocate idle disk slices to high-priority metadata storage units, ensuring system operability even when slice resources are limited.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If disk slices are allocated for reconstructing storage units, then reconstruction can proceed, but if metadata storage units go offline, user data storage units become inaccessible

Engineering Contradiction:

Improvestorage unit availabilityVSAvoiduser data accessibility

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system takes preliminary action to prevent metadata storage units from going offline by assigning them the highest reconstruction priority. Before any user data storage unit can be affected by metadata unavailability, the system ensures metadata storage units are reconstructed first using available idle disk slices. This preliminary protection of metadata integrity prevents the cascading failure that would make user data inaccessible.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system performs preliminary classification of storage units into different priority levels before reconstruction begins. Metadata storage units are pre-identified and assigned high priority, ensuring they receive reconstruction resources first. This preliminary organization allows the system to proactively protect critical metadata availability, preventing the scenario where user data becomes inaccessible due to metadata loss.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If all available idle disk slices are used for reconstruction, then more disk slices can be restored, but no slices remain for future malfunction scenarios

Engineering Contradiction:

Improvereconstructed disk slicesVSAvoidfuture fault tolerance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The system applies partial action by not reconstructing all possible storage units simultaneously, but rather selecting only the most critical ones (metadata storage units with high priority) for reconstruction. This partial approach ensures that limited idle disk slices are allocated to the most important storage units, maintaining future fault tolerance while still restoring critical functionality. The system avoids excessive reconstruction that would exhaust all slices and leave no capacity for future failures.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11481275B2Managing reconstruction of a malfunctioning disk slice

Publication Date: 2022.10.25 EMC IP HLDG CO LLC

AI summary

Techniques involve: determining, according to a determination that a performance level of a target storage unit is lower than a threshold level, whether idle disk slices that can be used for reconstructing malfunctioning disk slices in the target storage unit exist in a slice pool; determining a priority of the target storage unit according to a determination that the idle disk slices do not exist; and selecting replacing disk slices for reconstructing the malfunctioning disk slices from available storage units based at least in part on the priority, wherein the available storage units have performance levels not lower than the threshold level. In this way, data loss due to the off-line of storage units is prevented; and meanwhile, the performance of the entire storage system can be globally stabilized.