Thinly Provisioned File System Incremental Formatting
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Solution Overview
Problem
Extending thinly provisioned file systems in prior systems is time-consuming due to the need to fully format newly added space before it can be used, leading to potential timeouts and NO-SPACE errors, even when sufficient underlying storage is available.
Innovation Solution
The method involves adding newly extended space to the file system in batches and formatting it incrementally as it is used, allowing file I/O requests to be satisfied using the formatted initial portion without waiting for the entire space to be formatted, thus avoiding timeouts and NO-SPACE errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the file system formats all newly extended space before allowing file I/O operations, then storage space reservation is guaranteed, but file I/O operations experience timeouts and NO-SPACE errors
Solution Approach 1:
The file system performs preliminary formatting of only the initial portion of newly extended space before allowing file I/O operations to proceed. This preliminary action provides enough formatted space to satisfy current I/O requests while avoiding the time loss associated with formatting the entire extended space upfront. Subsequent formatting occurs incrementally in the background without blocking I/O operations.
2Reliability
If the file system waits for complete formatting of newly extended space, then all storage locations are guaranteed to be usable, but dense file extension operations may fail with NO-SPACE errors
Solution Approach 1:
The file system applies partial formatting action by formatting only the initial portion of newly extended space that is needed to satisfy current file I/O requests, rather than formatting the entire extended space. This partial action allows dense file extensions to proceed successfully without waiting for complete formatting, thereby improving productivity while maintaining sufficient reliability for current operations.
3Productivity
If the file system formats newly added space incrementally as it is used, then I/O operations complete faster, but there is a risk of running out of formatted space
Solution Approach 1:
The file system maintains continuous useful action by performing incremental formatting of newly extended space in the background as I/O operations proceed. This continuous background formatting ensures that formatted space is continuously replenished to meet ongoing I/O demands, maintaining both high productivity (fast I/O completion) and reliability (sufficient formatted space availability) simultaneously.
Data Source
AI summary
A data storage system operates a file system as a thinly provisioned file system having a host-visible virtual space and a smaller allocated space of underlying physical storage from a pool. The file system applies formatting to the allocated space and utilizes formatted allocated space for storing host files. The file system receives a file I/O request that requires increasing the allocated space of the file system, and in response (1) obtains an extent of physical storage from the pool and adds it to the file system as added allocated space, and (2) formats an initial portion of the added allocated space and satisfies the file I/O request using the formatted initial portion. Over a subsequent period the file system incrementally formats additional portions of the added allocated space and satisfies subsequent file I/O requests from the added portions.