A: By default, the I/O load-balancing algorithm used by Storage DRS is invoked every eight hours. You might think this is a relatively long period of time; however, recall that Storage DRS's load balancing requires quite a bit more activity than does virtual machine (VM) load balancing with traditional DRS. Entire disk files must be migrated between volumes for a Storage vMotion to complete, a process that takes far longer than relocating VM memory for a traditional vMotion.
VMware recommends against changing the invocation period from its default. A longer period reduces the impact of Storage DRS's activities, but could lead to greater imbalance. On the other hand, the increased activities associated with a shorter period could have an impact on VM performance.