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Many people have suggested that writing 1 byte is not efficient and writing more bytes should be faster. I tried it both with write-caching on and off.
I was using The writes were done at 0 and 512 byte offsets into the file, and the whole experiment was repeated 5 times. The best time is shown for each point. Each data point represents only a small number of writes, though, so the error may be high. Also, the "x1" machine for some of the tests; the other machines were is my laptop, so it wasn't always idle.