> It is. Actually, that's the best thing about running MySQL on ZFS. The doublewrite buffer is not just another form of overhead
There has been an interesting discussion on the MariaDB mailing list, questioning this, called "Is disabling doublewrite safe on ZFS?"¹.
The last post has been from the InnoDB lead, saying²:
> I believe that it is technically possible for a copy-on-write filesystem like ZFS to support atomic writes, but for that to be possible in practice, the interfaces inside the kernel must be implemented in an appropriate way.
It seems even he is not 100% sure on this topic.