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I have been working a lot with the Windows VI Toolkit lately, it is a very straight forward way of working with your Virtual Infrastructure programmatically.

One of the things I have noticed is that there are a few cmdlets, that are exceedingly slow.  These cmdlets aren’t so bad to use if you are working with a single VM, but if you start doing some scripting against hundreds or thousands of machines, whoa boy – I mean hit enter, go make a cup of coffee, drink it, drop the kids off at the pool, and you’ll still have time to spare.

Thus far the worst cmdlets I’ve come across are get-vm and get-harddisk.  get-vmhost, and get-cluster are pretty pokey as well, but fortunately even in a large environment, there aren’t that many hosts and there are even fewer clusters so they don’t annoy me with their pokeyness much.  Yet.

Here’s an example of how slow these cmdlets are, I have a script that I wrote that looks at my VI, and grabs every single VM that fits a certain naming pattern, which business rules dictate are VDI instances.  Next, I take the VM collection, and pull some interesting data: name, memory allocation, guestOS, IP, VLAN (portgroup), and VMDK size.  I knew from the get go that get-vm was slow, so I was using get-view.  get-view doesn’t return quite as friendly an object, but if you are willing to explore, it has everything you need.

So my collection of ~1200 VMs, comes back, and I do a little dance with it, then I get the portgroup:

$tempvm.vlan = (Get-View -Id $vm.network).name fairly speedy return

Then I get the VMDK size:

get-harddisk -VM $vm.name | foreach-object -process {$tempvm.diskGB += $_.CapacityKB}
    $tempvm.diskGB = [math]::round(($tempvm.diskGB / 1048576),0)
    if ($tempvm.diskGB -eq 0)
    {
        $tempvm.diskGB = “N-A”
    }

Let’s jsut say you can go take a nice nap, but it returns the total size of the VMDKs attached to the system.

I then scheduled this script to run via AutoSys, and it happily generated a CSV of all my VDI instances, and the info I wanted – in 35 hours!

I was a bit perturbed by the run time, but figured it was a batch job, and I could adjust the start times, and I’d just live with it.

Not any longer!  Today I had an epiphany of sorts while exploring the get-view object returned for a VM – it was if the skies had parted, God spoke to me, while a chorus of Angels sang.  Or I could have seen a Narwhal, I’m not really sure, but it was that cool.

The epiphony caused me to modify two lines of code – the temp.vlan line, and the get-harddisk line – replacing them with:

foreach ($device in ($myvm.config.hardware.device)) {if ($device.backing.devicename -like “VLAN*”) {$tempvm.vlan=$device.backing.devicename}}

and

foreach ($device in ($vm.config.hardware.device)) {if ($device.backing.filename -like “*vmdk”){$tempvm.diskGB += $device.capacityinKB}}

After the changes, I force started my job and waited eagerly for it to complete – 2 minutes and 15 seconds later.  Same result, only 35 hours less of waiting.

And if you don’t believe me, here is the run log from AutoSys

Original Code:

Revised Code: