How Can I Optimize C Binary File Writes for Maximum SSD Performance?

Writing Large Buffers to Binary Files in C : Optimizing Performance

The Original Question:

When attempting to write large amounts of data (80GB) to an SSD, the provided C code using std::fstream achieved speeds of approximately 20MB/s, significantly slower than the expected transfer rates of an SSD. The question seeks methods to optimize the writing process.

The Solution:

Option 1: Using std::fstream with sync_with_stdio(false)

This approach utilizes std::fstream with the sync_with_stdio(false) flag, which disables synchronization between C and C I/O streams. By uncoupling the streams, it improves performance on some systems by reducing the overhead of formatting and flushing data.

Option 2: Leveraging C Standard I/O Functions

This option employs low-level C standard I/O functions (fopen, fwrite, and fclose) for writing data to the binary file. C I/O operates at a lower level than std::fstream, offering greater control over file operations and potentially higher performance.

Updated Measurements:

To determine the effectiveness of each approach in present-day scenarios, revised code and measurements were conducted in 2017:

Code:

The updated code employs more advanced techniques, such as data generation, synchronization with the high-resolution clock, and flexible buffer size manipulation.

Results:

The measurements revealed that both Option 1 (using std::fstream with sync_with_stdio(false)) and Option 3 (using C standard I/O functions) fully utilized the SSD's write capabilities, achieving similar write speeds.

Conclusion:

The best approach for writing large buffers to binary files in C depends on specific hardware and software configurations. In general, std::fstream with sync_with_stdio(false) and C standard I/O functions provide efficient performance. By eliminating bottlenecks, these techniques allow for optimized and fast data transfer to SSDs.

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