Sorry for the late reply, just spotted your comment. Thanks for the input, glad you found it useful! Regarding the benchmark, the physical block size of the d

Sorry for the late reply, just spotted your comment. Thanks for the input, glad you found it useful! Regarding the benchmark, the physical block size of the drive itself was 512 bytes. The memory page size on the Ubuntu system was 4K. It would be good to update the benchmark script to include these kinds of numbers. I'm not sure why O_DIRECT speed increased with block size=4K (60MB/s) to 8K (90MB/s) and tapered off at 16KB (130MB/s). Perhaps system call overhead is more noticeable at 4K and 8K and less so at 16KB? Any other ideas? 130MB/s is the raw drive write speed and matches what I got from dd for the same flags for the same drive.