xPerf: Once I Was Blind and Now I See

I’ve been aware of the buzz around xPerf for quite some time.  I flagged emails from Microsoft Premier Field Engineers Clint Huffman (author of PAL) & Shane Creamer (author of Vital Signs) who in internal DLs both cited the tool way back in 2008.

Robert Smith is also a Microsoft PFE.  He is one of Microsoft’s leading engineers for troubleshooting SANs & other challenges related to disk I/O subsystems.  He is the author of the ground-breaking KB 929491 on disk partition alignment.

And on top of all that, Robert is also an xPerf expert.

xPerf is the lightweight tool used to capture information from the kernel-based Event Tracing for Windows (ETW).  Perhaps you’ll soon be as enthusiastic a supporter as I.

Recently, Robert Smith was generous enough to volunteer some time for a demo.  He shared insights which continue to amaze me, showing me how to interpret performance metrics such as:

  • Discrete reads & writes
  • Discrete I/O size, concurrency, & serial vs. random
  • Size of discrete I/Os
  • Random writes vs. serial writes (e.g., to a log file)

And perhaps most importantly:

  • Identify definitive latencies at Windows vs. storage
  • Identify time spent at the driver level (e.g., storport.sys, ntfs.sys, & kernel.sys)

Raise your hand if you’ve ever had an I/O bottleneck & your SAN man says, “Hey, sorry you’re having problems, but everything’s good on our end, we even talked to our vendor…” 

xPerf allows us to answer definitively, unequivocally, & without question whether it’s your server, your SAN, or both.


Such granularity & related aggregations has been heretofore unavailable to me.  I believe xPerf will fundamentally change the way I do my job.

Stay tuned for additional details.  I intend to share information to help you get started, tips, tricks, & techniques such as Robert shared & a few of my own, & case studies.

Principal Performance Engineer: SQL Server
A.C.E.: Assessment Consulting & Engineering Services
Don’t practice in front of the CIO.  A professional prepares ahead of time.
     —Pond's 12th Law

Comments (4)

Cancel reply

  1. Chuck says:

    If Jimmy is excited about something, then so am I.  Thank you very much, sir, for sharing this.

  2. SJB says:

    Raises hand!  

    Really looking forward to these series of blogs.  xPerf is one of those things I keep thinking "must learn that", but never get to.

  3. JL says:

    Is this tool only available in Win7 SDK?

  4. Jimmy May says:

    The distribution mechanism has indeed changed since this post.  However, you needn’t download & install the multiple GB file.  I have documented step-by-step instructions here:




    From time-to-time I’ll be posting additional guidance, including practical use cases & other news you can use.

Skip to main content