Disk mapping Windows/VMware

Since I’m working in a datacenter department at a service provider automation is a big thing. We have lots of different automatic workflows already. Everything from reading out power usage for co-location customers to creating a fully functional virtual datacenter with VMware vCloud Director.

The latest idea was to create an automatic disk expansion service. We monitor the customer’s environments with PRTG and call to help them with an expansion when more disk space is needed. But that’s only within business hours and of our service desk are busy we don’t always make the expansion in a timely fashion. For an exchange server, this is bad, full-disk means no mail flow.

Our backend developer(super skilled guy) extended the service agent that we run on all customer servers, with a new data collector that looks for free space and disk-identifiers. If a disk is running full he will create a RabbitMQ ticket that will trigger a vRealize Orchestrator workflow that finds the disk and expands it. Then reports back to his services so that his service can expand the disk from within Windows.

Identifying Windows disk from VMware environment

Our google foo was giving the same result over and over again, we should look at the SCSI ID. From within Windows, you can get the LUN ID and what controller its located. That position should then be the same as seen from VMware side.

While testing it on Windows 2016+ this worked ok. BUT we have customers that are still on Windows 2012, and here it didn’t work. *Sigh*. If the VM where having multiple controllers then we could not see what UnitId were to attach to the corresponding Controller Id. So back to the drawing board.

### From VMs Id and ControllerId and UnitId the disk that needs expansion is found. 
#$vmDisk = (Get-VM -Id $vmid | Get-HardDisk) | where { $_.ExtensionData.ControllerKey -eq ((Get-VM -id $vmid | Get-ScsiController ).ExtensionData | where { $_.BusNumber -eq $ControllerId }).Key } | where { $_.ExtensionData.UnitNumber -eq $SCSITargetId }

### Afterwards the disk can have the added capacity.
$vmDisk | Set-HardDisk -CapacityGB ($vmDisk.CapacityGB + $ExpandSizeGb) -Confirm:$false

We then kept looking but could not find anything in particular. Thinking about a physical disk having a serial number we began to pursue that idea, the VM should see the UUID that VMware where presenting. And yes, this sure seems to be working a Windows 2008 through Windows 2019.

VMware VM extension data – UUID

With the disk serial number approach, it was also easier to find the disk.

### UUID can be found in the VM extension data.
$vmDisk = (Get-VM -Id $vmid | Get-HardDisk) | Where-Object {$_.ExtensionData.Backing.uuid.Replace("-","") -eq $disksn } 

Conclusion:

Don’t know why other people are not suggesting the disk serial number approach instead of the SCSI ID. But my theory is that many looks at what data they can get from the vCenter GUI. And here the SCSI ID based on controller id and unit id is the only thing really available.

But there is a lot of nice data when using PowerCLI to look at the data. Especially when doing automation.