While I respect Brendan I think the arguments he makes are kinda weak. For example take OpenZFS. OpenZFS on Linux or FreeBSD isn't that great;
OpenZFS on Linux is only an option if you want to support the compatibility. As long as OpenZFS can't have (parts) inside the main Linux kernel source tree there is going to be breakage on updates. Which means manually testing and maintaining updates. Or you have to confine yourself to Ubuntu because they are of the opinion you can combine the CDDL and GPL. Don't think Ubuntu indemnifies you against an Oracle lawsuit though.
You could use FreeBSD as an alternative. FreeBSD is great, but lacks a lot of functionality. For example a good I/O scheduler is missing in FreeBSD. The FreeBSD I/O scheduler will basically just do what is most advantageous for it. If you have competing I/O workloads which you want to serve "fairly" there is no way to do that on FreeBSD. Basically the load which "pulls the hardest gets the most".