FreeBSD and Linux SSD Write Speeds

Adam Vande More amvandemore at
Wed Jun 21 16:45:52 UTC 2017

On Wed, Jun 21, 2017 at 11:04 AM, Tim Daneliuk <tundra at>

> Disclaimer: Tests below run on lightly loaded systems, but results are ...
> surprising:
> Test Case: dd if=/dev/zero of=foo bs=8M count=512
> Linux 4.4.0-21-generic on a 2.66GHz Core2 Duo w/8GB memory, older OCZ
> SSD/ext4:  310MB/sec writes
> FreeBSD 10-STABLE on an 3.2 GHz Quad Core i5 w/8GB memory, newer Kingston
> SSD/ufs:  210MB/sec writes
> Results are repeatable.
> So, what is the likely culprit making FreeBSD 1/3 slower?  The FreeBSD
> system does does / nfs exported (which I don't quite yet understand since
> all the nfs mount points are below it) at the moment, but there is little
> or no nfs traffic.

SSD speeds can vary greatly based upon models.  What steps did you take to
ensure the rates you are seeing aren't completely normal?


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