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DiskSpd is a storage performance tool from the Windows, Windows Server and Cloud Server Infrastructure engineering teams at Microsoft. Please visit for updated documentation.

In addition to the tool itself, this repository hosts measurement frameworks which utilize DiskSpd. The initial example is VM Fleet that was used for the Windows Server 2016 Hyper-Converged Storage Spaces Direct work.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.


The Releases page includes pre-compiled binaries (ZIP) and source code for the most current releases of the DiskSpd tool. The latest update to DiskSpd can be downloaded from

What's New?


DISKSPD 2.0.21a 9/21/2018

  • Added support for memory mapped I/O:
    • New -Sm option to enable memory mapped I/O
    • New -N<vni> option to specify flush options for memory mapped I/O
  • Added support for providing Event Tracing for Windows (ETW) events
  • Included a Windows Performance Recorder (WPR) profile to enable ETW tracing
  • Added system information to the ResultParser output

DISKSPD 2.0.20a 2/28/2018

  • Changes that may require rebaselining of results:
    • New random number generator that may show an observable decreased cost
    • Switched to 512-byte aligned buffers with the -Z option to increase performance
  • New -O option for specifying the number of outstanding IO requests per thread
  • New -Zr option for per-IO randomization of write buffer content
  • XML: Adds a new <ThreadTarget> element to support target weighting schemes
  • Enhanced statistics captured from IOPS data
  • Added support for validating XML profiles using an in-built XSD
  • Added support for handling RAW volumes
  • Updated CPU statistics to work on > 64-core systems
  • Updated calculation and accuracy of CPU statistics
  • Re-enable support for ETW statistics

DISKSPD 2.0.18a 5/31/2016

  • update /? example to use -Sh v. deprecated -h
  • fix operation on volumes on GPT partitioned media (:)
  • fix IO priority hint to proper stack alignment (if not 8 byte, will fail)
  • use iB notation to clarify that text result output is in 2^n units (KiB/MiB/GiB)

DISKSPD 2.0.17a 5/01/2016

  • -S is expanded to control write-through independent of OS/software cache. Among other things, this allows buffered write-through to be specified (-Sbw).
  • XML: adds a new <WriteThrough> element to specify write-through
  • XML: <DisableAllCache> is no longer emitted (still parsed, though), in favor or <WriteThrough> and <DisableOSCache>
  • Text output: OS/software cache and write-through state are now documented separately (adjacent lines)
  • Latency histogram now reports to 9-nines (one part in one billion) in both text and XML output
  • Error message added for failure to open write-content source file (-Z<size>,<file>)

VM Fleet

VM Fleet 0.9 10/2017 (minor)

  • watch-cpu: now provides total normalized cpu utility (accounting for turbo/speedstep)
  • sweep-cputarget: now provides average CSV FS read/write latency in the csv

VM Fleet 0.8 6/2017

  • get-cluspc: add SMB Client/Server and SMB Direct (not defaulted in Storage group yet)
  • test-clusterhealth: flush output pipeline for Debug-StorageSubsystem output
  • watch-cluster: restart immediately if all child jobs are no longer running
  • watch-cpu: new, visualizer for CPU core utilization distributions

VM Fleet 0.7 3/2017

  • create/destroy-vmfleet & update-csv: don't rely on the csv name containing the friendlyname of the vd
  • create-vmfleet: err if basevhd inaccessible
  • create-vmfleet: simplify call-throughs using $using: syntax
  • create-vmfleet: change vhdx layout to match scvmm behavior of seperate directory per VM (important for ReFS MRV)
  • create-vmfleet: use A1 VM size by default (1VCPU 1.75GiB RAM)
  • start-vmfleet: try starting "failed" vms, usually works
  • set-vmfleet: add support for -SizeSpec for A/D/D2v1 & v2 size specification, for ease of reconfig
  • stop-vmfleet: pass in full namelist to allow best-case internal parallelization of shutdown
  • sweep-cputarget: use %Processor Performance to rescale utilization and account for Turbo effects
  • test-clusterhealth: support cleaning out dumps/triage material to simplify ongoing monitoring (assume they're already gathered/etc.)
  • test-clusterhealth: additional triage output for storport unresponsive device events
  • test-clusterhealth: additional triage comments on SMB client connectivity events
  • test-clusterhealth: new test for Mellanox CX3/CX4 error counters that diagnose fabric issues (bad cable/transceiver/roce specifics/etc.)
  • get-log: new triage log gatherer for all hv/clustering/smb event channels
  • get-cluspc: new cross-cluster performance counter gatherer
  • remove run-<>.ps1 scripts that were replaced with run-demo-<>.ps1
  • check-outlier: EXPERIMENTAL way to ferret out outlier devices in the cluster, using average sampled latency

VM Fleet 0.6 7/18/2016

  • CPU Target Sweep: a sweep script using StorageQoS and a linear CPU/IOPS model to build an empirical sweep of IOPS as a function of CPU, initially for the three classic small IOPS mixes (100r, 90:10 and 70:30 4K). Includes an analysis script which provides the linear model for each off of the results.
  • Update sweep mechanics which allow generalized specification of DISKSPD sweep parameters and host performance counter capture.
  • install-vmfleet to automate placement after CSV/VD structure is in place (add path, create dirs, copyin, pause)
  • add non-linearity detection to analyze-cputarget
  • get-linfit is now a utility script (produces objects describing fits)
  • all flag files (pause/go/done) pushed down to control\flag directory
  • demo scripting works again and autofills vm/node counts
  • watch-cluster handles downed/recovered nodes gracefully
  • update-csv now handles node names which are logical prefixes of another (node1, node10)

Source Code

The source code for DiskSpd is hosted on GitHub at:

Any issues with DiskSpd can be reported using the following link:


DISKSPD is a storage load generator / performance test tool from the Windows/Windows Server and Cloud Server Infrastructure Engineering teams




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