Log-Structured File System Virtual Volume Capacity Management
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Solution Overview
Problem
In storage systems using a Log-Structured File system (LFS) with virtual volumes, frequent updates lead to early allocation of storage medium capacities as data is written to multiple areas, resulting in inefficient use of resources.
Innovation Solution
The storage system writes update data to unused areas behind a write cursor and reuses areas ahead of it, dynamically managing capacity allocation based on actual data usage and available storage medium capacity to prevent premature allocation of virtual volume capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LFS writes update data to multiple areas on a virtual volume, then data update performance is maintained, but storage medium capacity is allocated early and used up
Solution Approach 1:
The patent implements dynamic capacity allocation for virtual volumes by tracking the write cursor position and adjusting the allocated capacity accordingly. Instead of allocating fixed capacity upfront, the system dynamically expands capacity only to the extent needed for current write operations, preventing premature allocation while maintaining LFS update performance
Solution Approach 2:
The system changes the parameter of virtual volume capacity from a static fixed value to a dynamic value that adjusts based on the write cursor position and actual data usage. This allows the capacity allocation to adapt to the actual needs of LFS operations, allocating more capacity only when write operations require it
2Adaptability or versatility
If thin-provisioning delays capacity allocation until input/output requests are issued, then virtual volume capacity exceeds physical storage capacity, but LFS writes to multiple areas causing early capacity consumption
Solution Approach 1:
The system performs preliminary tracking of the write cursor position and predicts future write destinations before actual write operations occur. By monitoring the write cursor and identifying areas that will be written to, the system can pre-allocate capacity only for those specific areas, avoiding both premature full allocation and insufficient allocation
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring the write cursor position and actual write operations on the virtual volume. Based on this feedback, the system adjusts capacity allocation dynamically, expanding capacity only to areas where writes are occurring or about to occur, thereby preventing early capacity consumption while maintaining flexibility
Data Source
AI summary
In the present invention, when configuration data art a LFS (Log-Structured File system) is stored on a virtual volume constructed from a plurality of Storage mediums, a temporal change of the file size on the file system is roughly estimated. Then, in accordance with the change, a capacity that is needed on the virtual volume is provided, a cursor at the end of a log is set, and a write cursor for writing data is set so as to avoid the position behind the cursor at the end of the log. Accordingly, it is possible to, when the LFS occupies only a small area on the virtual volume, avoid early execution of the allocation of an available capacity, and thus avoid a circumstance in which a large number of storage mediums are needed at an early stage of the operation of the virtual volume (see FIG. 1).