I have made a function to set reservations on VM´s in PowerCLI. The function takes a VM as parameter and also percentage of CPU and Memory you want to reserve.

The function checks the Mhz of the physical CPU from the Host the VM is running on and makes the reservation from this.

In the function I can set both memory and cpu reservation or just one of them

here is a screendump of the function being used

and here is the PowerCLI

function Set-VMReservation{
<#
.SYNOPSIS
Set VM Reservation on Memory and/or CPU

.DESCRIPTION
Use this function set VM reservations 

.PARAMETER MemoryMB
Use this parameter to set the percent of memory reserved for the VM

.PARAMETER CpuMhz
Use this parameter to set the percent of CPU Mhz from the host CPU to be reserved

.NOTES
Author: Niklas Akerlund
Date: 2012-07-19
#>
    param (
   [Parameter(Position=0,Mandatory=$true,HelpMessage="A VM",
    ValueFromPipeline=$True)]
    $VM,
	$MemoryMB = 0,
	$CpuMhz = 0
    )
	$VM = Get-VM $VM
	if ($MemoryMB -ne 0 -and $CpuMhz -ne 0){
		$MemoryMB = $MemoryMB/100
		[int]$MemoryMB = $VM.MemoryMB*$MemoryMB
		$CpuMhz = $CpuMhz/100
		[int]$CpuMhz = ([math]::truncate(((Get-VMHost -id $VM.extensiondata.summary.runtime.host).ExtensionData.Hardware.CpuInfo.hz)/1000000))*$VM.NumCpu*$CpuMhz
		$VM | Get-VMResourceConfiguration |Set-VMResourceConfiguration -CpuReservationMhz $CpuMhz -MemReservationMB $MemoryMB
	}elseif ($MemoryMB -ne 0 -and $CpuMhz -eq 0){
		$MemoryMB = $MemoryMB/100
		[int]$MemoryMB = $VM.MemoryMB*$MemoryMB
		$VM | Get-VMResourceConfiguration |Set-VMResourceConfiguration -MemReservationMB $MemoryMB
	}elseif ($MemoryMB -eq 0 -and $CpuMhz -ne 0){
		$CpuMhz = $CpuMhz/100
		[int]$CpuMhz = ([math]::truncate(((Get-VMHost -id $VM.extensiondata.summary.runtime.host).ExtensionData.Hardware.CpuInfo.hz)/1000000))*$VM.NumCpu*$CpuMhz
		$VM | Get-VMResourceConfiguration |Set-VMResourceConfiguration -CpuReservationMhz $CpuMhz
	}elseif ($MemoryMB -eq 0 -and $CpuMhz -eq 0){
		$VM | Get-VMResourceConfiguration |Set-VMResourceConfiguration -CpuReservationMhz 0 -MemReservationMB 0
	}
}

In this example I have set the CPU reservation to 60 % and Memory to 40 %

A colleague wanted a script that could make a Host-VM affinity rule so that certain VM´s that resided on one storage at one site would run on the hosts on that site, the cluster spanns over two sites so the VM´s can run at both sites but one datastore is primary at the first site and the other at the second site.  So He wanted to get the VM´s that have their storage on datastoreLocation1 to be in an host-vm affinity rule “Should Run” on the hosts that is in that site. In this community post I found most of the code, I made som adjustments but mostly the cred goes to @lucd22 and GotMoo.

Here you can see the screendump from the cluster settings

Here is the powerCLI that has been run

One thing here was also that this VMgroup should be updated once a day if there was new VM´s that needed to be included. So this lines should be run in a scheduled task, this will make the DRSVMGroup VMLocationDC1 to be updated with the VM´s currently located at that datastore:

$VM = get-datastore delad02 | get-vm
Update-DrsVMGroup -cluster vmw* -VMs $VM -groupVMName VMLocationDC1

Here are the PowerCLI functions for doing this. As you can see I have an switch parameter for -MustRun, that will create the rule as a Must Run on these hosts.

function New-DRSGroupRule{
<#
.SYNOPSIS
Create a new DRSGroupRule for VMs to reside on some hosts in a cluster

.DESCRIPTION
Use this function to create vms in a group and hosts in a group and a host-vm affinity

.PARAMETER  MustRun
A switch that will create the rule with Must Run on these host, if not set it will create the rule with should run.

.NOTES
Author: Niklas Akerlund / RTS (most of the code came from http://communities.vmware.com/message/1667279 @LucD22 and GotMoo)
Date: 2012-06-28
#>
	param (
	[Parameter(Position=0,Mandatory=$true,HelpMessage="A Cluster",
	ValueFromPipeline=$True)]
	$cluster,
	$VMHosts,
	$VMs,
	[string]$Name,
	[switch]$MustRun
	)
	
	$cluster = Get-Cluster $cluster

	$spec = New-Object VMware.Vim.ClusterConfigSpecEx
	$groupVM = New-Object VMware.Vim.ClusterGroupSpec 
	$groupVM.operation = "add" 
	$groupVM.Info = New-Object VMware.Vim.ClusterVmGroup
	$groupVM.Info.Name = "VM$Name"

	Get-VM $VMs | %{
	$groupVM.Info.VM += $_.Extensiondata.MoRef
	}
	$spec.GroupSpec += $groupVM

	$groupESX = New-Object VMware.Vim.ClusterGroupSpec 
	$groupESX.operation = "add"
	$groupESX.Info = New-Object VMware.Vim.ClusterHostGroup
	$groupESX.Info.Name = "Host$Name"

	Get-VMHost $VMHosts | %{
	$groupESX.Info.Host += $_.Extensiondata.MoRef
	}
	$spec.GroupSpec += $groupESX

	$rule = New-Object VMware.Vim.ClusterRuleSpec
	$rule.operation = "add"
	$rule.info = New-Object VMware.Vim.ClusterVmHostRuleInfo
	$rule.info.enabled = $true
	$rule.info.name = $Name
	if($MustRun){
		$rule.info.mandatory = $true
	}else{
		$rule.info.mandatory = $false
	}
	$rule.info.vmGroupName = "VM$Name"
	$rule.info.affineHostGroupName = "Host$Name"
	$spec.RulesSpec += $rule

	$cluster.ExtensionData.ReconfigureComputeResource($spec,$true)
}

function Update-DrsVMGroup {
<#
.SYNOPSIS
Update DRS VM group with a new collection of VM´s

.DESCRIPTION
Use this function to update the ClusterVMgroup with VMs that are sent in by parameters

.PARAMETER  xyz 

.NOTES
Author: Niklas Akerlund / RTS (most of the code came from http://communities.vmware.com/message/1667279 @LucD22 and GotMoo)
Date: 2012-06-28
#>
	param (
	$cluster,
	$VMs,
	$groupVMName)
	
    $cluster = Get-Cluster $cluster
    $spec = New-Object VMware.Vim.ClusterConfigSpecEx
    $groupVM = New-Object VMware.Vim.ClusterGroupSpec 
    #Operation edit will replace the contents of the GroupVMName with the new contents seleced below.
    $groupVM.operation = "edit" 

    $groupVM.Info = New-Object VMware.Vim.ClusterVmGroup
    $groupVM.Info.Name = $groupVMName 

    Get-VM $VMs | %{
        $groupVM.Info.VM += $_.Extensiondata.MoRef
    }
    $spec.GroupSpec += $groupVM

    #Apply the settings to the cluster
    $cluster.ExtensionData.ReconfigureComputeResource($spec,$true)
}

When I get the time I might add some more functionality to also remove rules and groups.

I made a blog post some time ago, where i created a powerCLI function for creating a VM affinity rule that would keep my VM´s in a vApp together in the cluster for better VM-VM performance. I then checked for MoRef to get the VM correlated between vCloud Director and vCenter.

The answer to my problem was much closer than I thought, the vCloud director creates a folder in the “VM´s and Template view” for each vApp and guess what, all VM´s are in there.. so I do not need to ask the vCloud Director anymore (well if I want the Cloud vApp name I do need to ask it..) but ironically I had not looked there and found out that the folders actually where created for each deployed vCloud vApp :-/

So the code is a bit simpler and to get all VM´s from a folder I just type this, the asterisk is because the folder also gets a unique id

Get-Folder | where {$_.Name -like "ProdvCPod*"} | Get-VM

And then I just need to put those VM´s into an array and create a DRS rule, and here is the function that does this

<#
.Synopsis
   Add an affinity rule for a vCloud Director vAPP
.DESCRIPTION
   This function takes a vApp name (string) as parameter and creates an affinity rule for them to keep them together
.EXAMPLE
   Add-vAppAffinity -CIVApp ProdCust01
.NOTES
Author: Niklas Akerlund
Date: 2012-06-21
#>
function Add-vAppAffinity
{
    Param
    (
        # Parameter for the vAPP
        [Parameter(Mandatory=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=0)]
        $CIVApp,

        # If the rule should apply on a different cluster
        $Cluster = "Cluster01"
    	)

	if ($CIVApp -ne " " -or $CIVApp -ne $null -or $CIVApp.length -ne 0 ){
		$Cluster = Get-Cluster $Cluster
		$VAppname = $CIVApp + "*"
		$VMs =  Get-Folder | where {$_.Name -like $VAppname} | Get-VM	
		
		if (!(Get-DrsRule -Cluster $Cluster -Name $CIVApp -ErrorAction SilentlyContinue)){ 
			New-DrsRule -Name $CIVApp -Cluster $Cluster -KeepTogether $true -VM $VMs
		}else{
			Remove-DrsRule -Rule (Get-DrsRule -Cluster $Cluster -Name $CIVApp) -Confirm:$false
			New-DrsRule -Name $CIVApp -Cluster $Cluster -KeepTogether $true -VM $VMs
		}
	}
}

To run it:

and it looks something like this if I check the cluster settings

preferably you have set your DRS cluster to fully automated or not so much will happen 🙂