Using vscsiStats to collect IO and Latency stats on Virtual Disks

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides steps for finding IO and Latency stats on Virtual Disks.

Environment

VMware vSphere ESXi

Resolution

Instructions on using vscsiStats to collect IO and Latency stats on Virtual Disks.

1. Run this command to find the world ID of the virtual machine you want to watch:
   /usr/lib/vmware/bin/vscsiStats -l
   
   
   Output example:
   Virtual Machine worldGroupID: VM_ID1, Virtual Machine Display Name: vm_name {
   Virtual SCSI Disk handleID: 8192
   }
   Virtual Machine worldGroupID: VM_ID2, Virtual Machine Display Name: vm_name {
   Virtual SCSI Disk handleID: 8193
   }
   Virtual Machine worldGroupID: VM_ID2, Virtual Machine Display Name: vm_name {
   Virtual SCSI Disk handleID: 8196
   Virtual SCSI Disk handleID: 8197
   }
   Virtual Machine worldGroupID: VM_ID3, Virtual Machine Display Name: vm_name {
   Virtual SCSI Disk handleID: 8204
   }
   
   
2. Run this command to start the recording:
   /usr/lib/vmware/bin/vscsiStats -s -t -w worldGroupID_from_step_1
   
   Note: This impacts virtual machine performance.
   
   The output appears similar to:
   vscsiStats: Starting Vscsi stats collection for worldGroup VM_ID1, handleID 8193
   vscsiStats: Starting Vscsi cmd tracing for worldGroup VM_ID1, handleID 8193
   <vscsiStats-traceChannel>vscsi_cmd_trace_VM_ID1_8193</vscsiStats-traceChannel>
   Success.
   
   
3. Check the IOs and latency histogram:
   /usr/lib/vmware/bin/vscsiStats -p latency -w worldGroupID_from_step_1
   
   The output appears similar to:
   Histogram: latency of IOs in Microseconds (us) for virtual machine worldGroupID : VM_ID1, virtual disk handleID : 8193 {
   min : 5355
   max : 10604
   mean : 7376
   count : 4
   {
   0 (<= 1)
   0 (<= 10)
   0 (<= 100)
   0 (<= 500)
   0 (<= 1000)
   0 (<= 5000)
   4 (<= 15000)
   0 (<= 30000)
   0 (<= 50000)
   0 (<= 100000)
   0 (> 100000)
   }
   }
   Histogram: latency of Read IOs in Microseconds (us) for virtual machine worldGroupID : VM_ID1, virtual disk handleID : 8193 {
   min : 0
   max : 0
   mean : 0
   count : 0
   {
   0 (<= 1)
   0 (<= 10)
   0 (<= 100)
   0 (<= 500)
   0 (<= 1000)
   0 (<= 5000)
   0 (<= 15000)
   0 (<= 30000)
   0 (<= 50000)
   0 (<= 100000)
   0 (> 100000)
   }
   }
   Histogram: latency of Write IOs in Microseconds (us) for virtual machine worldGroupID : VM_ID1, virtual disk handleID : 8193 {
   min : 5355
   max : 10604
   mean : 7376
   count : 4
   {
   0 (<= 1)
   0 (<= 10)
   0 (<= 100)
   0 (<= 500)
   0 (<= 1000)
   0 (<= 5000)
   4 (<= 15000)
   0 (<= 30000)
   0 (<= 50000)
   0 (<= 100000)
   0 (> 100000)
   }
   }
   
   
4. Run this command to stop the stats collection:
   /usr/lib/vmware/bin/vscsiStats -x -w worldGroupID_from_step_1

Additional Information

https://blogs.vmware.com/vsphere/2014/10/vmware-virtual-san-performance-testing-part-iii.html