Overview of disk I/O performance

With the ever-increasing density of physical ESXi hosts hosting virtual machines, it is easy to understand the increase in disk I/O activity across the server's disk subsystem. This, coupled with certain application workloads that are sensitive to I/O latency, makes this a resource to watch.

When you consider all the resources (computer, memory, storage, and networking) that are needed to create the vSphere environment, storage is normally the slowest resource and in some cases, it is a complex resource to understand. When storage problems, such as bottlenecks occur, they are most likely to have a negative impact on virtual machines.

Most storage performance issues can be the result of a configuration problem (or the result of investing in the wrong HW), and care should be taken during the installation or updating of the storage environment. Using the highest performing disks and controllers with top speed connections will improve the storage performance...