[danford]

I wasn't using zfs at the time and I didn't do much comparison with CPU and IO, I used a wattage meter. I followed the FreeBSD guide (http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/ac...) and tried just about everything. My Linux box was running at about 9watts (idle) and freeBSD started out at around 18, but I got it down to about 12watts after making a lot of optimizations.

I think most of the difference is because FreeBSD is using older more stable software, and the Ubuntu server was running some of the latest software.

[takeda]

Do you remember which FreeBSD version and which Linux kernel version was it?

Linux had tickless kernel + CPU scaling for a while. FreeBSD is lagging in this aspect.

[profquail]

The FreeBSD kernel is tickless as of FreeBSD 10:

http://www.freebsdnews.net/2013/09/20/freebsd-10s-new-techno...

[takeda]

Yes, exactly, it only has it for couple of months, that's why I asked about version.