Identifying storage contention and performance issues

One of the biggest causes of poor storage performance is quite often the result of high I/O latency values. Latency in its simplest definition is a measure of how long it takes for a single I/O request to occur from the standpoint of your virtualized applications. As we will find out later, vSphere further breaks the latency values down into more detailed and precise values based on individual components of the stack in order to aid us with troubleshooting.

But is storage latency always a bad thing? The answer to that is "it depends". Obviously, a high latency value is one of the least desirable metrics in terms of storage devices, but in terms of applications, it really depends on the type of workload we are running. Heavily utilized databases, for instance, are usually very sensitive when it comes to latency, often requiring very low latency values before exhibiting timeouts and degradation of performance.

There are however other applications...