With both Linux and FreeBSD being open source, I am curious what is it that prevents ZFS from being a first-class, stable component in Linux right now, just as it already is in FreeBSD.
ZFS's license (CDDL) is generally considered incompatible with Linux's (GPLv2), whereas it's compatible with the BSD license. See https://sfconservancy.org/blog/2016/feb/25/zfs-and-linux/, which also discusses the case of Ubuntu moving towards including it by default anyhow.
Maybe it's fixed with this version, but we've seen kernel pauses on the order of minutes under high memory / OOM situations, with ZoL trying to get memory.
What was your setup like? I've encountered similar - the cause ended up being a mix of xattrs (I don't use them so I just disabled the feature) and needing to tune zfs to be less aggressive handling my consumer-grade disks.
Can you expand on what you did to tune things?
I run a 10 disk raidz2 array on a box with 4G RAM. If I'm running many other things on that box, memory gets very tight, and it swaps occasionally too. I've not seen kernel pauses on FS accesses though.
My understanding is that potential licensing incompatibilities is what has kept ZFS from being (tightly) integrated into linux: