Useless Use of "dd" (2015)
While there’s a lot of truth here, there are times when you can do much better than cat. A while back I tweeted:<p>Today I found the magical dd command that causes an NVMe drive to run at almost full speed:<p><pre><code>  # dd if=&#x2F;dev&#x2F;nvme3n1 bs=4096k iflag=direct of=&#x2F;dev&#x2F;null status=progress
  959090524160 bytes (959 GB, 893 GiB) copied, 178 s, 5.4 GB&#x2F;s
</code></pre>
The trick to getting this throughput is telling Linux to do an insanely large IO (4 MiB). The drive can&#x27;t do 4 MiB reads - the largest IO it can handle is 2 MiB.<p><pre><code>  # nvme id-ctrl &#x2F;dev&#x2F;nvme3 | grep mdts
  mdts      : 9
  # echo &#x27;4 \* 2^9&#x27; | bc -l
  2048
</code></pre>
More in the tread starting here:<p><a href="https:&#x2F;&#x2F;twitter.com&#x2F;OMGerdts&#x2F;status&#x2F;1514376206082269191?s=20&amp;t=6YcJZRCQIgeV4m1DU5OvRQ" rel="nofollow">https:&#x2F;&#x2F;twitter.com&#x2F;OMGerdts&#x2F;status&#x2F;1514376206082269191?s=20...</a>