Using vscsiStats to collect IO and Latency stats on Virtual Disks
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Article ID: 310655
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Updated On: 04-10-2025
Products
VMware vSphere ESXi
Issue/Introduction
This article provides steps for finding IO and Latency stats on Virtual Disks.
Resolution
Instructions on using vscsiStats to collect IO and Latency stats on Virtual Disks.
-
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
}
-
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.
-
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)
}
}
-
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
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