Excellent post by Robert Smith, PFE: 

Introduction

Performance problems, especially as they may relate to the storage subsystem, can be quite difficult to troubleshoot.  Enterprise storage technology has come a long way since the SCSI controller with an array of disks.  Fortunately, there are some great tools available to help narrow down where to look more closely for storage performance problems.  This blog post covers the Windows Performance Analysis Toolkit (WPT), as used for analyzing performance in the storage subsystem.

The facility that enables the analysis I am about to cover is called "Event Tracing for Windows" (ETW).  The Performance Analyzer is built on top of the ETW infrastructure. ETW enables Windows and applications to efficiently generate events, which can be enabled and disabled at any time without requiring system or process restarts. ETW collects requested kernel events and saves them to one or more files referred to as "trace files" or "traces." These kernel events provide extensive details about the operation of the system. Some of the most important and useful kernel events available for capture and analysis are context switches, interrupts, deferred procedure calls, process and thread creation and destruction, disk I/Os, hard faults, processor P-State transitions, and registry operations, though there are many others.

One of the great features of ETW, supported in WPT, is the support of symbol decoding, sample profiling, and capture of call stacks on kernel events. These features provide very rich and detailed views into the system operation. WPT also supports automated performance analysis. Specifically, xperf is designed for scripting from the command line and can be employed in automated performance gating infrastructures (it is the core of Windows PerfGates). xperf can also dump the trace data to an ANSI text file, which allows you to write your own trace processing tools that can look for performance problems and regressions from previous tests.

The following information will be mostly about the WPT tool called "Xperf.exe".  Xperf.exe is the command line tool used to start, stop, and manage traces.  The usage of Xperf.exe is documented thoroughly in the help file included with the WPT titled "WindowsPerformanceToolkit.chm".

 Read the full post here: http://blogs.technet.com/b/robertsmith/archive/2012/02/07/analyzing-storage-performance-using-the-windows-performance-toolkit.aspx