Database Node Fencing via Metadata Authorization
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Solution Overview
Problem
Existing methods for isolating malfunctioning database nodes in clustered database systems are either complex or require external intervention, particularly in distributed systems where data is shared across multiple discs and controllers, such as the SCSI Fencing approach, which is not effective.
Innovation Solution
A database system that fences out a malfunctioning node by preventing it from updating the catalog and writing to allocated storage regions, using a metadata server to maintain an authorization identifier and instructing shared storage to block write operations, thereby isolating the node without relying on external mechanisms like physical power-down or complex SCSI commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external intervention mechanisms like SCSI Fencing or physical power-down are used to isolate malfunctioning nodes, then node isolation reliability is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent introduces a metadata server as an intermediary component that maintains authorization identifiers and mediates access control between database nodes and shared storage. This mediator handles the complexity of node isolation internally, allowing malfunctioning nodes to be fenced out through software-based authorization checks rather than requiring complex external fencing mechanisms like SCSI Fencing or physical power-down procedures.
Solution Approach 2:
The system implements self-service fencing by having the metadata server automatically manage authorization identifiers and enforce access control policies. When a node malfunctions, the system automatically updates authorization identifiers to prevent the malfunctioning node from accessing shared storage, eliminating the need for external intervention or complex manual fencing procedures.
2Reliability
If complex external fencing mechanisms are implemented to prevent data corruption, then data integrity is improved, but ease of operation and system simplicity deteriorate
Solution Approach 1:
The metadata server acts as an intermediary that simplifies data integrity protection by centralizing authorization management. Instead of requiring operators to implement complex external fencing mechanisms, the metadata server automatically manages authorization identifiers and enforces access control, making the system easier to operate while maintaining data integrity.
Solution Approach 2:
The patent replaces mechanical or external fencing mechanisms (like SCSI Fencing or physical power-down) with a software-based authorization system. The metadata server uses authorization identifiers to control node access to shared storage, substituting complex mechanical fencing operations with simpler software-based access control that is easier to operate and maintain.
3Measurement precision
If authorization identifiers are maintained centrally in a metadata server, then node access control precision is improved, but system complexity increases
Solution Approach 1:
The metadata server performs multiple functions: it maintains the catalog of shared storage portions, manages authorization identifiers, and enforces access control policies. By consolidating these functions in a single component, the system achieves precise access control without proportionally increasing overall system complexity, as the metadata server handles multiple responsibilities efficiently.
Data Source
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AI summary
Techniques are disclosed relating to fencing out a first one of a plurality of nodes configured to handle requests for data stored in a distributed storage. A database system, in various embodiments, stores a value indicating that the first node is permitted to update a catalog stored at a metadata server. In response to a determination to prevent the first node from updating the catalog and writing to the distributed storage, in various embodiments, the database system updates the value to indicate that the first node is not permitted to update the catalog and instructs the distributed storage to prevent write operations to a particular portion allocated to the first node for writing data.