I recently been faced on a classical problem on InnoDB which is the fragmentation, but on Galera. InnoDB engine doesn’t defragment on the fly and requires optimize maintenance sometimes to free disk space. But on Galera, which is a fault tolerance and high availability solution, it’s a problem having tables locked by an optimize procedure. Until Galera doesn’t support TokuDB and only fully support InnoDB, we had (with a colleague (Kevin aka Vinek)) to find a solution.