Metadata Server Dangling Directory Check for Distributed Storage
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Solution Overview
Problem
Distributed storage servers face challenges in preventing collisions such as deadlock and namespace inconsistency during complex operations like rename operations, which require communication with multiple servers and can lead to transaction blocking and instability.
Innovation Solution
A distributed storage server system where a selected metadata server checks for dangling directories before processing rename operations, ensuring exclusive processing and maintaining namespace consistency by setting and releasing rename-exclusive locks, and communicating with other servers to verify directory existence and lock sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rename operations are processed by multiple metadata server devices concurrently, then processing throughput is improved, but collision (deadlock, namespace inconsistency) occurs between servers
Solution Approach 1:
The system performs preliminary actions by checking for dangling directories and acquiring rename-exclusive locks before processing rename operations. The metadata server device checks whether a dangling directory occurs by performing the rename operation in advance, and only processes the transaction if no dangling directory is detected. This preliminary validation prevents collisions and namespace inconsistencies while allowing concurrent processing to proceed.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a rename-exclusive lock that mediates access to metadata during rename operations. The selected metadata server device acquires this lock before checking for dangling directories and processing the rename operation, ensuring exclusive access and preventing collisions with other servers while maintaining system throughput.
2Reliability
If rename operations require communication with several servers, then operation completeness is improved, but transaction blocking and deadlock occur
Solution Approach 1:
The system performs preliminary validation by checking for dangling directories and acquiring necessary locks before initiating communication with multiple servers. The metadata server device checks whether parent directories exist and whether the rename operation would create dangling directories in advance, preparing all necessary conditions before actual transaction processing begins.
Solution Approach 2:
The patent applies preliminary anti-action by checking for potential problems (dangling directories, missing parent directories) before executing the rename operation. The system detects and prevents potential deadlocks and transaction blocking by validating the operation path and acquiring exclusive locks beforehand, rather than encountering these issues during actual server communication and transaction execution.
3Reliability
If dangling directory checks are performed before transaction period, then namespace consistency is improved, but processing time is increased
Solution Approach 1:
The system performs the dangling directory check as a preliminary action before the transaction period begins. The metadata server device checks whether a dangling directory occurs by performing the rename operation in advance, during the preparation phase rather than during transaction execution. This timing separates validation from execution, ensuring namespace consistency while optimizing processing efficiency.
Data Source
AI summary
A distributed storage server includes a plurality of data server devices and a plurality of metadata server devices. The metadata server devices store metadata associated with data which is distributively stored in the data server devices. A selected metadata server device checks whether a dangling directory occurs by performing a rename operation, based on information associated with a full path of a parent directory of a source and a full path of a parent directory of a target included in a request of the rename operation. When it is determined that the dangling directory does not occur, the selected metadata server device processes transactions directed to the metadata such that the rename operation is performed. The checking whether the dangling directory occurs is performed before a transaction period for processing the transactions.