Postgres heavily relies on various parts of the operating system - filesystem and buffered i/O are good examples of such fundamental dependencies. But there are many commonly used filesystems supported by Linux, from traditional ones (ext4,xfs) to modern ones (zfs, btrfs) and various exotic ones. The question is - are there significant performance differences between these filesystems for Postgres? Are there clear winners or filesystems you definitely should not use? I did a similar comparison a couple years back, but both the Postgres and kernel are continuously improving and adopting to new hardware, so let's look at fresh data.