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    Profile, don't speculate! Commented Mar 17, 2011 at 23:30
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    Interestingly, their benchmarks suggest there is little benefit above 4K however. Commented Mar 18, 2011 at 1:24
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    Also, apparently the default file read ahead window is 128 KB, so that value might be beneficial. Commented Mar 18, 2011 at 1:33
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    I have access to a 24 drive RAID50 here, where bs=8K gets me 197MB/s but bs=1M gets me 2.2 GB/s which is close to the theoretical throughput of the RAID. So bs matters ALOT. However using bs=10M I only get 1.7GB/s. So it appears to get worse over some threshold, but not sure why. Commented Nov 2, 2015 at 18:22
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    @JosephGarvin Yes, I always find it worthwhile to play around a bit with the block size if I'm doing a large transfer. It seems the optimum block size depends on a lot of different things. Commented May 6, 2017 at 21:01