This document describes how to benchmarkPersistent Disk performanceon Windows virtual machine (VM) instances. For Linux VMs, seebenchmark Persistent Disk performance on a Linux VM.

Tomeasure IOPS and throughput of a disk in use on a running instance,benchmark the file system with its intended configuration. Use this option totest a realistic workload without losing the contents of your existing disk.Note that when you benchmark the file system on an existing disk, there are manyfactors specific to your development environment that may affect benchmarkingresults, and you may not reach thedisk performance limits.

Tomeasure the raw performance of a Persistent Disk, benchmark theblock device directly. Use this option to compare raw disk performance to diskperformance limits.

OnC4 VMs, Windows supportsa maximum depth of 1024 per device submission queue. When a queue fills, Windowsstops submitting I/O until the queue has partially drained, which significantlyreduces performance. To avoid triggering this condition, we recommendlimiting your benchmarking workloads to an aggregate queue depth of 1024 perattached volume.

Configure benchmarking software

To benchmark Persistent Disk performance on Windows VMs, useDISKSPD.

1. Connect to your VM instance.

2. Open Powershell and download theDISKSPD tool using the following command:

   $client = New-Object System.Net.WebClient$client.DownloadFile("https://github.com/Microsoft/diskspd/releases/latest/download/DiskSpd.zip","$env:temp\DiskSpd-download.zip")Expand-Archive -LiteralPath "$env:temp\DiskSpd-download.zip" C:\DISKSPDGet-ChildItem C:\DISKSPD

   Note: You can also download the latest version of theDISKSPD tool directlyfromGitHub and extract it manually.

Benchmark IOPS and throughput of a disk on a running VM instance

To measure IOPS and throughput for a realistic workload on an activedisk on a running VM instance without losing the contents of your disk, benchmarkagainst a new directory on the existing file system.

In the following steps assume the disk to test is mounted asD: and thecommands are executed in aCommand Prompt (cmd.exe) window that hasadministrator privileges:

1. Connect to your VM.

2. VerifyDISKSPDsoftware configuration and changedirectory to the 64-bit binary:

   Note: The following command assumesDISKSPD was installed atC:\DISKSPD.

   cd C:\DISKSPD\amd64

3. Create a new 10 GB file namedDISKTEST.DAT on the disk:

   set TESTFILE=D:\DISKTEST.DATdiskspd -d0 -c10G %TESTFILE%

4. Test write throughput by performing sequential writes with multipleparallel streams (16 or more), using an I/O block size of 1 MB and an I/O depthof at least 64:

   diskspd -d300 -b1M -o64 -Sh -w100 -t16 -si %TESTFILE%

5. Test write IOPS by performing random writes, using an I/O block size of4 KB and an I/O depth of at least 256:

   diskspd -d300 -b4K -o256 -Sh -w100 -r %TESTFILE%

6. Test read throughput by performing sequential reads with multiple parallelstreams (16 or more), using an I/O block size of 1 MB and an I/O depth of atleast 64:

   diskspd -d300 -b1M -o64 -Sh -t16 -si %TESTFILE%

7. Test read IOPS by performing random reads, using an I/O block size of4 KB and an I/O depth of at least 256:

   diskspd -d300 -b4K -o256 -Sh -r %TESTFILE%

8. Clean up:

   del %TESTFILE%

Benchmarking raw Persistent Disk performance

To measure the performance of Persistent Disk volumes alone outside ofyour development environment, test read and write performance for a blockdevice on a throwaway Persistent Disk and VM.

1. Create and start a VM instance.

2. Add a Persistent Disk to the VM instancethat you intend to benchmark.

3. Connect to your VM instance.

4. VerifyDISKSPDsoftware configuration and changedirectory to the 64-bit binary:

   Note: The following command assumes DISKSPD was installed at C:\DISKSPD.

   cd C:\DISKSPD\amd64

5. Verify that there are no non-reserved partitions on the disk. Enterdiskpart into an elevatedCommand Prompt window.

   diskpart

6. List the disks attached to the VM:

   DISKPART>list disk

   The output shows the newly created 1 TB disk which is Disk 1 in thefollowing example output:

     Disk ###  Status         Size     Free     Dyn  Gpt  --------  -------------  -------  -------  ---  ---  Disk 0    Online          120 GB  1024 KB        *  Disk 1    Online         1024 GB  1023 GB        *

7. Select the disk that you intend to benchmark.

   DISKPART>select disk 1

8. List the partitions on the selected disk.

   DISKPART>list partition

      Partition ###  Type              Size       Offset   -------------  ----------------  --------   -------   Partition 1    Reserved              15 MB    17 KB   Partition 2    Primary             1024 GB    16 MB

9. Select the primary partition 2:

   DISKPART>select partition 2

10. Delete the selected partition:

    DISKPART>delete partition

    Warning: This step will cause permanent loss of data.

11. Exit diskpart

    DISKPART>exit

The preceding steps should be repeated if the disk you intend to benchmarkhas any other partitions apart from the Reserved partition. When only theReserved partition remains, continue with the following steps:

1. After you've identified the disk and verified that there are no partitions,set theTESTDRIVE environment variable to '#' followed by the number of thedisk to test.

   C:/>set TESTDRIVE=#1

2. Test write throughput by performing sequential writes with multipleparallel streams (16 or more), using an I/O block size of 1 MB andan I/O depth of at least 64:

   diskspd -d300 -b1M -o64 -Sh -t16 -si -w0 %TESTDRIVE%

3. Test write IOPS by performing random writes, using an I/O block size of4 KB and an I/O depth of at least 256:

   diskspd -d300 -b4K -o256 -Sh -r -w0 %TESTDRIVE%

4. Test write latency. While testing I/O latency, the VM must not reachmaximum bandwidth or IOPS; otherwise, the observed latency won't reflectthe actual Persistent Disk I/O latency.

   diskspd -d300 -b4K -o4 -Sh -r -w0 -L %TESTDRIVE%

5. Test read throughput by performing sequential reads with multiple parallelstreams (16 or more), using an I/O block size of 1 MB and an I/O depthof at least 64:

   diskspd -d300 -b1M -o64 -Sh -t16 -si %TESTDRIVE%

6. Test read IOPS by performing random reads, using an I/O block size of4 KB and an I/O depth of at least 256:

   diskspd -d300 -b4K -o256 -Sh -r %TESTDRIVE%

7. To test read latency, it's important to fill the disk with data to get arealistic latency measurement. The VM must not reach IOPSor throughput limits during this test because after the Persistent Diskreaches its saturation limit, it pushes back on incoming I/O operations,and this is reflected as an artificial increase in I/O latency.

   diskspd -d300 -b4K -o4 -Sh -r -L %TESTDRIVE%

8. Test sequential read bandwidth.

   diskspd -d300 -b1M -o64 -Sh -t4 -si %TESTDRIVE%

9. Test sequential write bandwidth.

   diskspd -d300 -b1M -o64 -Sh -t4 -si -w100 %TESTDRIVE%

10. Clean up the throwaway Persistent Disk and VM:

    1. Delete the disk used forbenchmarking performance.
    2. Delete the VM createdfor benchmarking performance.

What's next

• Learn how to monitor your disk performance byreviewing persistent disk performance metrics.
• Learn aboutPersistent Disk pricing.
• Learn how tooptimize Persistent Disk performance.