==================================Migration speed accounting in Hbal==================================.. contents:: :depth: 2Hbal usually performs complex sequence of moves during cluster balancing inorder to achieve local optimal cluster state. Unfortunately, each move may takesignificant amount of time. Thus, during the sequence of moves the situation oncluster may change (e.g., because of adding new instance or because of instanceor node parameters change) and desired moves can become unprofitable.Usually disk moves become a bottleneck and require sufficient amount of time.:ref:`Instance move improvements <move-performance>` considersdisk moves speed in more details. Currently, ``hbal`` has a ``--no-disk-moves``option preventing disk moves during cluster balancing in order to perform fast(but of course non optimal) balancing. It may be useful, but ideally we need tofind a balance between optimal configuration and time to reach thisconfiguration.Avoiding insignificant disk moves=================================Allowing only profitable enough disk moves may become a first step to reacha compromise between moves speed and optimal scoring. This can be implementedby introducing ``--avoid-disk-moves *FACTOR*`` option which will admit diskmoves only if the gain in the cluster metrics is *FACTOR* timeshigher than the gain achievable by non disk moves.