How to set disk IOPS limit using govc?

[Heiko-san]

Hi,

What I want to achieve is to set the IOPS limit for the disk of an existing vm.
I mean the setting that goes into vm's config as "sched.scsi0:0.throughputCap=xy", which you set in GUI by "edit settings" -> go to the disk -> "Limit IOPs" -> if you switch to "user defined" you can enter any number ...

• I found govc vm.disk.change but it seems I can only set disk size there.
• I see the disk using govc device.info -vm myvm disk-1000-0
• There is also a govc disk.ls, but it doesn't show anything

How can I set this limit?

Update:

• I found this, but doesn't seem to work either (even if it doesn't show any errors): govc vm.change -vm myvm -e sched.scsi0:0.throughputCap=123

[embano1]

Is extraConfig what you're looking for? https://github.com/vmware/govmomi/blob/master/govc/USAGE.md#vmchange

[Heiko-san]

I actually tried this (see above, the "-e" switch).

[embano1]

Sorry, my bad :( Can you confirm that setting the extended attribute changes the vmx or doesn't it do anything at all?

[Heiko-san]

It seems to do nothing at all, the parameter I tried is the one that appears in the vmx file, if I configure the limit in the GUI.
But setting it with "-e" neither sets it in vmx file, nor is the limit shown if I edit the VM in the GUI.

On the other hand: If I download the vmx file, set the parameter in the file, upload it again and restart the VM ... The setting is still not reflected if I edit the VM in GUI.
So maybe it's not a govmomi issue, maybe it's just the wrong way of doing this. (? I'm not that familiar with the vmware API)

[embano1]

I think I found the reason. The extraConfig way might not be used anymore (though the UI seems to set the value for backwards compat?). Anyways, I found that the API to use is this one.

If you look at the VM configuration you'll find this configuration:

"StorageIOAllocation": {
              // -1 is unlimited, respectively the value you specify via API/UI
              "Limit": -1,
              "Shares": {
                "Shares": 1000,
                "Level": "normal"
              },
              "Reservation": 0
            }

Currently govc does not allow to specify this property so the only way is to use the govmomi library currently. See #396 for related discussion.

[embano1]

I created a draft PR for govc: #2807

[Heiko-san]

cool, thanks a lot :)

[embano1]

Np, can you please mark this discussion as answered then so it‘s resolved?

[Heiko-san]

Stupid question: How? :P I can't find a button or something to resolve it/ mark it as answered. :|

[embano1]

Alright, I was wondering the same (and thought only you could do it as author). Let me lock the conversation then. Perhaps a bug in Github.

[tenthirtyam]

Moved to Q&A and marked as answered.