According to official requirements from Microsoft, SQL Server 2019 only supports either ext4 or xfs. I suspect that a Copy-On-Write filesystem such as btrfs or zfs may hurt the performance of the database. There can be bugs and other compatibility issues as well.
What if I create a zvol and format it with xfs, then put the database on top of the xfs filesystem? Theoretically, SQL Server daemon only knows that it is working with the xfs, without knowing what are actually beneath it. What can I expect in such scenario?
The same applies to QEMU qcow2 format. It neither likes btrfs nor zfs because it is already Copy-On-Write by itself. What if I put it on a zvol formatted with ext4? Does the performance suffer?
