FreeBSD and Linux SSD Write Speeds

[Warren Block]

On Wed, 21 Jun 2017, Tim Daneliuk wrote:

> 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.

Is Linux doing write caching?  They used to do that.