Good post by Colm Keegan (thank you)
Maintaining consistent application performance has become increasingly challenging. While there are fewer physical servers to support in the data center, in many environments there are dozens, hundreds or even thousands of virtual machines (VMs) accessing the same shared storage resources. This typically results in increased storage I/O latency as highly randomized read and write operations from multiple VMs bombard shared storage; otherwise knows as the “storage I/O blender” effect.
Read on here