Have you done any writing about that experience and setup? Both Postgres and ZFS are COW, I seem to recall some warnings back in the day about conflicts between the two systems but I have no first hand experience.
I've seen ZFS being used with Postgres in a few different environments. Seems to work fine for the most part- surprisingly good compression (~8X in one case, usually lower), with the major downside being increased CPU usage when taking advantage of said compression.
I think that only one or two of those environments were heavily used production instances, so if there is a serious gotcha here it might not have been apparent to me.
No we’re kind of a lean shop so we don’t do much tech blogging - it’s something we’re thinking of doing soon though.
As for CoW, we just turn it off on the postgres config and rely strictly on ZFS. We also turned off checksumming and compression in postgres and use Zstd:3 on the file system. Beyond that we just followed your run of the mill tuning guide you’d find on Google.
