We are looking to use mysql or mariadb within docker on zfs.
I've seen a few old articles that seem to suggest that you need some special configuration options for zfs.
https://github.com/docker-library/mysql/issues/57
disable innondb aio https://hub.docker.com/r/vvoronin/mysql-zfs/dockerfile/
However all these discussions are quite old so I'm unsure if this is still an issue?
Is it safe to run mysql/docker/zfs? Are any configuration options required for it to be reliable?
Historical references seem to contain a few references to OSX, potentially some to WSL2. Consistent behavior from AIO and O_DIRECT though these layers isn't tested by MariaDB. I have no information if MySQL does so or not, so this is going to be a largely MariaDB answer.
The other zfs question you need to ask is is this zfs-fuse or OpenZFS.
MariaDB also doesn't test against any of these in CI (though a task exists to improve coverage).
Recent examples like MDEV-27900 show that btrfs, and O_DIRECT (and a bit of uring) can cause unexpected behaviour. This was quite quick to see on a test, however not all errors are as predicatable/repeatible.
Currently I'm working on MDEV-27593 improving AIO error handing.
fallocate seems to have a fallback implemented.
So for the moment for safety at least on MariaDB, I'd stick to --innodb_use_native_aio=0 and/or --innodb_flush_method=fsync for a little while longer to keep the stronger aspects of the zfs implementation used.
