To upgrade a ZFS storage pool version on FreeBSD, you can use the “zpool upgrade” command. The command will upgrade the specified pool to the most recent version supported by the system. For example:
zpool upgrade poolname
It is recommended to backup your data before upgrading. And also you may need to take the pool offline for a short time in order to do the upgrade.
zpool export poolname
zpool upgrade -V poolversion poolname
zpool import poolname
Where -V option is used to specify the version of pool you want to upgrade it to.
It’s important to note that once a pool is upgraded to a new version, it can no longer be accessed by older versions of the ZFS software, so you should make sure to upgrade all systems that access the pool to a version that supports the new pool version before upgrading the pool.