That blog post is wrong, it says that DRBD must be active/passive. But it has offered active/active for some time.

https://docs.linbit.com/doc/users-guide-83/s-dual-primary-mode/

The article mentions using CentOS, I believe. I'm not able to find the CentOS 7 packages -- they mentioned using the epel-releases, but my system doesn't seem to see it. Any ideas where to look? I'd really rather not have to resort to building it by hand.

Ubuntu has a PPA for it.