So if you are moving your data center to the next generation of Flash Storage you may have noticed your performance charts in VMware vCenter or other tools look something like this.
You start to think, what good is the millisecond scale in a microsecond world? (I know that screenshot is from vCOPS.)
Luckily VMware provided an answer (sorta kinda).
Using microsecond for Virtual Disk Metrics
Go ahead and select your VM and go to Monitor –> Performance and select Advanced.
First change the View from CPU to Virtual Disk(1).
Then select Chart Options(2)
Deselect the Legacy and move on to microseconds.
Then you can select Save Options to use these settings easily next time. The new settings will be saved in the drop down list in the top right corner.
Finally, you have a scale that can let you see what the Virtual Disks are doing for read and write latency.
Disk vs Virtual Disk Metrics
In the vSphere Online documentation the Disk Metric group is described as:
Disk utilization per host, virtual machine, or datastore. Disk metrics include I/O performance (such as latency and read/write speeds), and utilization metrics for storage as a finite resource.
While Virtual Disk is defined:
Disk utilization and disk performance metrics for virtual machines.
Someone can correct me if I am wrong, but the differences I see is even though they are both choices when a VM is selected only the Disk metric gives stats for the datastore device that the VM lives on and can be shown side by side with that VM’s stats but does NOT give the option to change the scale to microsecond if needed. Virtual Disk allows only VM level statistics but permits you to view them as microseconds at least for read and write latency.
Hope this helps.