We had similar issues with MongoDB on btrfs. While the snapshot features were nice, the write performance was abysmal. We moved to xfs at some point and got a m

We had similar issues with MongoDB on btrfs. While the snapshot features were nice, the write performance was abysmal. We moved to xfs at some point and got a massive increase in write throughput. So far I've worked at two separate companies deploying MongoDB into production and we've never had any real issues, mostly because in both cases the lead engineers really knew what they were doing, had read the manual front-to-back, and they knew exactly what kind of OS and filesystem setup to use for maximum effectiveness.