“The trust relationship between this workstation and the primary domain failed.”

The problem is detailed in this KB Article. What happens is that every 30 days (by default) the client initiates a computer password change on the domain controller. This computer password is used to authenticate the computer as the computer object in AD, and is distinct from the user’s password. When the non-persistent machine resets, the passwords go out of synchronization and domain authentication fails.

This can be fixed, as per Microsoft’s KB article, by disabling the client-initiated computer password changes; this can be done using Local or Group Policy, by script, or by directly editing the registry.

Using local, or group policy

Set the key shown below to Disabled

Using REGEDIT

Set the below value to 1

Using Windows shell script

 :: Set registry key to disable computer password expiry

REG ADD "HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters" /v DisablePasswordChange /t REG_DWORD /d 1 /f

If you’ve got access to the Domain Controller, you can also set a GPO so that Domain Controller: Refuse Machine Password Changes is Enabled. This is in Windows Settings à Securiy Settings à Local Policies à Security Options (the same location as the Domain Member: Disable Machine Account Password Changes).

Also, if you need to rejoin machines that have already fallen off the domain, you can miss the reboot after removing it from the domain, so:

1. Shut the machine down
2. Make the drives Persistent
3. Start the machine and log in
4. Remove the machine from the domain
5. Add the machine to the domain
6. Reboot
7. Shut-down and make Non-Peristent

Skipping the middle reboot saves a couple of minutes (which adds up if you have a lot to do). The above processes can also be scripted through the use of PowerCLI with Invoke-VMCommand and either NETDOM (for XP/Vista) or PowerShell for Windows 7.

At first, we manually changed these assignments using the Disk Management MMC before setting the drives to non-persistent. Lately, I’ve been using a DISKPART script, which speeds up the process, but still requires logging into each machine.

I saw Arnim van Lieshout’s post on Invoke-VMScript yesterday, and realised that this could be used to run the DISKPART script on multiple machines. In order to get the TXT file used by DISKPART onto the machine, I’m also using the Copy-VMGuestFile command found in PowerCLI 4.0 Update 1.

# Change drive letter assignment from D to Q
 
# Gets the specific VMs we're after as an object
$objVMs = Get-Folder "Sequencers" | Get-VM | Sort-Object Name
 
# Assign the command line required for DISKPART to a variable
$strScript = "IF EXIST D:\ DISKPART /S C:\DiskPart_Change_C_To_Q.txt"
 
# Loop through the VMs
ForEach ($objVM in $objVMs){
# Let the user know
Write-Host Copying file to $objVM
Copy-VMGuestFile -Source "C:\Tools\DiskPart_Change_C_To_Q.txt" -Destination "c:\" -LocalToGuest -VM $objVM -HostUser root -HostPassword password -GuestUser Administrator -GuestPassword password
Write-Host Changing disk partitions on $objVM
Invoke-VMScript $strScript -vm $objVM -HostUser root -HostPassword password -GuestUser Administrator -GuestPassword password -ScriptType "bat"
}

The TXT file contained the following:-

SELECT VOLUME 2
ASSIGN LETTER=Q

This requires root credentials for the host, and administrator rights on the target machine, but, as Arnim notes, will work in the absence of client network connectivity.

This is a bit of a hack,: leaving the TXT file behind on the C drive; using root credentials rather than an account with the least effective permissions; and having the script contain the credentials in plain-text. However, I’m enthusiastic about using this solution in a more structured way in future. I’m already thinking about using it to defragment and SDelete our thick-provisioned virtual machines before converting them to Thin provisioned disks.

Linked clones allow multiple machines to share a common read-only “base” VMDK file, with each machine generating their own delta (REDO). Under normal usage circumstances, the REDO would continue to grow throughout the life of the machine; however as our machines have non-persistent hard drives, they reset to a clean state when powered-down. This makes our environment ideally suited to taking advanatage of the functionality offered by Linked Clones. They can either be created manually (by moving and renaming files on the datastore), or via the APIs, you can get more information on them in this White Paper from VMware.

Our training machines are functionally identical to our production machines, and similarly consist of three types – Capture, Packaging and Verification. These are 11, 8, and 8 GB respectively. The usage patterns are slightly different, as – unlike “live” projects which have a steady stream of work, trainees tend to come in in large batches. This means that the training environment either needs to be continuously large, but mostly idle, or it needs to be regularly redeployed then stripped back.

The benefits achieved via the implementation of Linked Clones in this project resulted in roughly the same ratio of space saving as our proof-of-concepts, but as the number of machines involved was greater, the differences are more pronounced. Also this is the first time we’ve exceeded 8 machines sharing the same VMDK, which is a notable milestone as it is only possible if we limit the number of possible hosts that the machines can run on (there is a VMFS limitation of 8 hosts accessing a VMDK concurrently). As we have DRS enabled, this meant reducing the number of hosts in each cluster to 8 or less.

We deployed twenty-five machines each, of  the three different builds used in a project. All were Windows XP virtual machines

The three machines being used as the parents had their slack space on the drives was cleaned using SDelete, then the machine was converted to Thin Provisioned using Storage vMotion. It was switched off, and a snapshot was created. This snapshot will form the base for the parent’s clones.

The machines were deployed using the a script similar to the one at the bottom of this post, and it took just over an hour to deploy and customize all 75 machines. This was considerably faster than the time it would have taken to deploy 75 machines using the normal “Deploy from template”  method.

Here are the data:-

• Estimated space used if deployed traditionally: 675 GB
  • Capture: 11 GB per machine
  • Packaging: 8 GB per machine
  • Verification: 8 GB per machine

• Estimated Space if Deployed as Thin Provisioned, but not Linked Clones: 238.75 GB
  • Capture: 3.34 GB per machine
  • Packaging: 3.72 GB per machine
  • Verification: 2.49 GB per machine

• Space used in current configuration: 19.3 GB
  • Capture 3.34 GB for parent, plus 0.13 GB per Linked Clone
  • Packaging 3.72 GB for parent, plus 0.13 GB per Linked Clone
  • Verification 2.49 GB for parent, plus 0.13 GB per Linked Clone

And in graph-format, for extra impact:-

All size estimates are based on the machines in a powered-down state. When powered on, a swap file (equal to the size of the assigned RAM) is created, and (assuming the machines are non-persistent) REDO files are created on all types of machines.

I’ve been on a few of the machines and they don’t appear to suffer from any noticeable performance degradation, although the true test won’t come until we get considerable concurrent use.

I’m tentatively declaring this a huge success. Rather than the training environment using 240 GB between training engagaments, it’s now down to a svelte 20GB, with no reduction in functionality.

Below is a script similar to the one I used to deploy the linked clones. The actual “meat”, which deploys the machines was based on Hal Rottenberg’s New-LinkedClone.ps1 script. As far as possible, I’ve tried to strip out stuff that’s specific to our environment (we use the Custom Attributes as an asset management database and to track which machines were deployed from which templates). There’s probably going to be stuff in there that doesn’t make much sense, but if you’ve got a bit of an understanding of PowerShell, you should be able to cut and keep the bits you want.

# Script to deploy linked clones
 
# List of custom attributes which you're wanting to copy from the template or parent to the newly created machine
# (Machines deployed from templates no longer inherit CAs in vSphere 4.0)
# These help us track provenance, and provide information to the user
$arrStrAttributesToCopy = @(
"AD Object Location",
"Customisation",
"Infrastructure Consultant",
"Logon Administrator Name",
"Logon Administrator Password",
"Logon User Name",
"Logon User Password",
"Mobilisation Consultant",
"Project",
"Role",
)
 
# Name of the Custom Attribute on the parent which contains the name of the customisation to use
$CustomFieldName = "Customisation"
 
Function DeployLinkedClone ($strSourceVM, $intToBeDeployed, $intStartDeployingAtNumber, $CustomFieldName){
# Bases the name of the machine on the second part of the string split by spaces. This assumes that the template follows the standard naming convention of "Tmpl [Name] x.x"
$strMachinePrefix = ($strSourceVM.split(' ')[1])
$objVM = Get-VM $strSourceVM
$viewVM = $objVM | Get-View
$objCustomization = Get-OSCustomizationSpec ($objVM.CustomFields.Item($CustomFieldName))
# Ensure that the machines does not have a non persistent HD
If ($objVM | Get-HardDisk | Where-Object {$_.Persistence -like "IndependentNonPersistent"}){
Write-Host $objTemplate has a non-persistent HD!
}
# If the customisation, as specified in the parent's custom attribute does not exist, then quit.
If (!$objCustomization){
Write-Host Customisation ($objVM.CustomFields.Item($CustomFieldName)) not found. Exiting.
Break
}
$i = 1
Do {
# Convert the single digit integer (i.e., "1") into a double digit (i.e., "01")
$strMachineNumber = ("{0:0#}" -f $intStartDeployingAtNumber)
# Concatenate the machine name prefix (from the template name) with the double-digit integer, which is incrememted on each loop
$strMachineBeingDeployed = $strMachinePrefix+$strMachineNumber
# Check that the machine doesn't already exist
If ((Get-VM -Name $strMachineBeingDeployed -ErrorAction SilentlyContinue)){
Write-Host "Machine $strMachineBeingDeployed already exists!"
Break
}
# Let the user know what's going on
Write-Host ""
Write-Host "Deploying new linked-clone " -NoNewline
Write-Host $strMachineBeingDeployed -ForegroundColor Blue -NoNewline
Write-Host ", from template " -NoNewline
Write-Host $strSourceVM -ForegroundColor Blue -NoNewline
Write-Host ", using customisation " -NoNewline
Write-Host $objCustomization -ForegroundColor Blue -NoNewline
Write-Host ", on the same Host as the parent" -NoNewline
Write-Host ""
# Create the new machine using all these variables
$objFolder = $viewVM.parent
$specClone = New-Object Vmware.Vim.VirtualMachineCloneSpec
# Get the most recent snapshot attached to the machine
$specClone.Snapshot = $viewVM.Snapshot.CurrentSnapshot
# Create an object to represent the location of the clone
$specClone.Location = New-Object Vmware.Vim.VirtualMachineRelocateSpec
# This is the move-type that specifies the new disk backing (which is the bit that makes a linked clone)
$specClone.Location.DiskMoveType = "createNewChildDiskBacking"
# Run the task with the specified parameters
$task = $viewVM.CloneVM_Task($objFolder, $strMachineBeingDeployed, $specClone)
Get-VIObjectByVIView $task | Wait-Task | Out-Null
# Get the object for the machine which was just deployed
$objTargetVM = Get-VM $strMachineBeingDeployed
# Apply the customisation specification to the newly created clone
Set-VM -VM $objTargetVM -OSCustomizationSpec $objCustomization -Confirm:$false
# Start the clone
Start-VM -VM $objTargetVM
# Get the view (needed for writing custom attributes)
$viewTarget = $objTargetVM | Get-View
# Loop through each of the custom attributes which are to be copied
ForEach ($arrStrAttributeToCopy in $arrStrAttributesToCopy){
# Read the attribute from the source template
$objAttribute = $objVM.CustomFields.Item($arrStrAttributeToCopy)
# Apply the attribute to the machine object
$viewTarget.setCustomValue($arrStrAttributeToCopy,$objAttribute)
}
# Set the "Template" custom attribute to the parent templates
$arrStrAttributeToCopy = "Template"
$viewTarget.setCustomValue($arrStrAttributeToCopy,$strSourceTemplate)
# Increment the number used for naming the machines
$intStartDeployingAtNumber ++
# Increment the number used to count the number of machines deployed
$i ++
}
# Continue to loop while the number of machines deployed is less than the number required
While ($i -le $intToBeDeployed)
}
 
# Get the current time (for timing how long the script took to run)
$dteStart = Get-Date
 
# Name of source VM, should be persistent, should have a snapshot and the customisation specified in the nominated custom attribute
$strSourceVM = "Tmpl Capture 1.0"
# Number to be deployed
$intToBeDeployed = 25
# Number to start deploying from
$intStartDeployingAtNumber = 1
DeployLinkedClone $strSourceVM $intToBeDeployed $intStartDeployingAtNumber $CustomFieldName
 
# Name of source VM, should be persistent, should have a snapshot and the customisation specified in the nominated custom attribute
$strSourceVM = "Tmpl Packaging 1.0"
# Number to be deployed
$intToBeDeployed = 25
# Number to start deploying from
$intStartDeployingAtNumber = 1
DeployLinkedClone $strSourceVM $intToBeDeployed $intStartDeployingAtNumber $CustomFieldName
 
# Name of source VM, should be persistent, should have a snapshot and the customisation specified in the nominated custom attribute
$strSourceVM = "Tmpl Verification 1.0"
# Number to be deployed
$intToBeDeployed = 25
# Number to start deploying from
$intStartDeployingAtNumber = 1
DeployLinkedClone $strSourceVM $intToBeDeployed $intStartDeployingAtNumber $CustomFieldName
 
$dteEnd = Get-Date
$dteDiff = New-TimeSpan $dteStart $dteEnd
$timeTaken = [math]::round($dteDiff.totalMinutes, 2)
Write-Host ""
Write-Host "It took" $timeTaken "minutes for these machines to deploy"
 
# End of script

I passed the VCP on vSphere 4 just before Christmas with 463/500. At the time the deadline for taking the exam without having to the attend the What’s New was 31st December 2009, but that’s now been extended to the 31st January. It was nice to have it out of the way before Christmas though.

The exam seemed no more difficult than the VCP on VI 3; I think they even reused a few of the questions. I found the following useful:-

• Simon Long’s VCP vSphere 4 Practice Exams
• vSphere 4 Configuration Maximums
• Barry Coombs’ VMware vSphere cue-cards

Those sites also contain numerous links to other resources, so I’m sure you’ll find something which will suit your revision style.

Next on my to-do list is the Microsoft 70-431 Microsoft SQL Server 2005 – Implementation and Maintenance.

While it’s fairly specific to our use-case, I thought I’d share the details in case anyone else runs into this.

First of all, this bug will only affect you if the following conditions are met:

• You are using VMware vSphere 4.0 (or 4.0 Update 1)
• Guest OS power-saving settings cause the virtual machine to enter standby
• One or more of the guest’s hard drives are set to “independent non-persistent”
• DRS is enabled on the virtual machine’s cluster

The machine enters standby as normal. The issue arises when you try to power the virtual machine back on: if DRS has allocated the machine to another host based on load the machine will not resume, and gives an error similar to the following:-

“Virtual Machine is configured to use a device that prevents the operation: Device ‘Hard disk 1′ is disk which is not in persistent mode. Device ‘Hard disk 1′ which is not in persistent mode”.

You cannot manually migrate the machine (even back to the original host). You cannot change the power-state on the machine, edit the virtual machine settings, or delete the machine.

If this has happened to you, the only way we’ve found to get the machine back up-and-running seems to be to remove the machine from inventory, then create a new virtual machine with the same specifications, and add the old machine’s VMDK.

Fortunately, there are a couple of workarounds. You can either disable power-saving settings in the guest OS or change the guest power management settings from “Suspend the virtual machine” to “Put the guest OS into standby mode and leave the virtual machine powered on” (you can automate this as described in my previous post).

Changing the guest power-management settings means that when the guest enters standby, although vSphere shows the machine as “powered-on”, VMware Tools is not running, which can cause problems (i.e., when trying to gracefully shut down a batch of machines).

This was also my first time working with the VMware vSphere support and I was impressed. They quickly replicated the problem and confirmed that it was indeed a bug. As most people nowadays tend to use snapshots rather than non-persistent drives, and few users virtualise desktop operating systems (which are more likely to have power-saving settings on by default) I can understand why this particular set of circumstances went untested.

To do this the machines need to be powered down. We had an imminent maintenance window, but it wouldn’t allow us the time to make this change manually (even if we wanted to), this necessitated some automation. Unfortunately I had no idea how to go about editing this setting using the PowerCLI, even after a little search through the VMware PowerCLI community.

This seemed like the perfect opportunity to try out Project Onyx.

Carter Shanklin’s video does a good job of explaining how to Onyx up and running, and it worked exactly as described (even on my Windows 7 machine).

1. Download the Onyx files and extract to a folder
2. Run the Onyx executable



3. Click the Connect button, and connect to your VirtualCenter server.
4. Once that’s launched, start vSphere client, but instead of connecting to your VirtualCenter server, connect to http://localhost:1545 (Carter actually says 1445 in the video, but you can see on screen that he’s using 1545). Use your normal credentials.
5. Ignore the warning about unencrypted traffic (as Carter explains, the unencrypted traffic is local-only, the network traffic is still encrypted)
6. Click the Start button on Onyx
7. In vSphere client make whatever changes it is that you’re wanting to record.
8. Click the Pause button on Onyx, and you’ll see in the window a script has been created.
9. Copy this into your favourite PowerShell editor, and modify until it’s suitable for your purposes.

The original capture from the Onyx Window

$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
$spec.changeVersion = "2009-11-27T09:16:04.570821Z"
$spec.powerOpInfo = New-Object VMware.Vim.VirtualMachineDefaultPowerOpInfo
$spec.powerOpInfo.defaultPowerOffType = "soft"
$spec.powerOpInfo.defaultSuspendType = "hard"
$spec.powerOpInfo.defaultResetType = "soft"
$spec.powerOpInfo.standbyAction = "checkpoint"
 
$_this = Get-View -Id 'VirtualMachine-vm-1074'
$_this.ReconfigVM_Task($spec)

A second capture changing the setting back to isolate the exact line that makes the changes

$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
$spec.changeVersion = "2009-11-27T09:16:33.872017Z"
$spec.powerOpInfo = New-Object VMware.Vim.VirtualMachineDefaultPowerOpInfo
$spec.powerOpInfo.defaultPowerOffType = "soft"
$spec.powerOpInfo.defaultSuspendType = "hard"
$spec.powerOpInfo.defaultResetType = "soft"
$spec.powerOpInfo.standbyAction = "powerOnSuspend"
 
$_this = Get-View -Id 'VirtualMachine-vm-1074'
$_this.ReconfigVM_Task($spec)

And a finished script, which will run it against all machines in a specified blue folder comment/uncomment one of the $specVM.powerOpInfo.standbyAction lines to choose which option you want.

$objVMs = Get-Folder "Folder Name" | Get-VM
ForEach ($objVM in $objVMs){
	$specVM = New-Object VMware.Vim.VirtualMachineConfigSpec
	$specVM.powerOpInfo = New-Object VMware.Vim.VirtualMachineDefaultPowerOpInfo
	$specVM.powerOpInfo.standbyAction = "checkpoint" 			# Put the guest OS into StandBy Mode and leave the Virtual Machine powered On
	#$specVM.powerOpInfo.standbyAction = "powerOnSuspend" 		# Suspend the Virtual Machine
	$viewVM = Get-View -Id $objVM.Id
	$viewVM.ReconfigVM_Task($specVM)
}

I was actually surprised at how easy this was; and I think it’s going to make me a bit more adventurous with what I attempt to do via the PowerCLI.

The following enhancements have been made to ESX (from the release notes):-

VMware View 4.0 support – This release adds support for VMware View 4.0, a solution built specifically for delivering desktops as a managed service from the protocol to the platform.

Windows 7 and Windows 2008 R2 support –This release adds support for 32-bit and 64-bit versions of Windows 7 as well as 64-bit Windows 2008 R2 as guest OS platforms. In addition, the vSphere Client is now supported and can be installed on a Windows 7 platform. For a complete list of supported guest operating systems with this release, see the VMware Compatibility Guide.

Enhanced Clustering Support for Microsoft Windows – Microsoft Cluster Server (MSCS) for Windows 2000 and 2003 and Windows Server 2008 Failover Clustering is now supported on an VMware High Availability (HA) and Dynamic Resource Scheduler (DRS) cluster in a limited configuration. HA and DRS functionality can be effectively disabled for individual MSCS virtual machines as opposed to disabling HA and DRS on the entire ESX/ESXi host. Refer to the Setup for Failover Clustering and Microsoft Cluster Service guide for additional configuration guidelines.

Enhanced VMware Paravirtualized SCSI Support – Support for boot disk devices attached to a Paravirtualized SCSI ( PVSCSI) adapter has been added for Windows 2003 and 2008 guest operating systems. Floppy disk images are also available containing the driver for use during the Windows installation by selecting F6 to install additional drivers during setup. Floppy images can be found in the /vmimages/floppies/ folder.

Improved vNetwork Distributed Switch Performance – Several performance and usability issues have been resolved resulting in the following:

• Improved performance when making configuration changes to a vNetwork Distributed Switch (vDS) instance when the ESX/ESXi host is under a heavy load
• Improved performance when adding or removing an ESX/ESXi host to or from a vDS instance

Increase in vCPU per Core Limit – The limit on vCPUs per core has been increased from 20 to 25. This change raises the supported limit only. It does not include any additional performance optimizations. Raising the limit allows users more flexibility to configure systems based on specific workloads and to get the most advantage from increasingly faster processors. The achievable number of vCPUs per core depends on the workload and specifics of the hardware. For more information see the Performance Best Practices for VMware vSphere 4.0 guide.

Enablement of Intel Xeon Processor 3400 Series – Support for the Xeon processor 3400 series has been added. For a complete list of supported third party hardware and devices, see the VMware Compatibility Guide.

vCenter 4.0 has also been updated, and now has full compatibility with Windows 7 x86 and x64 versions. Saving the various hacks that were necessary to get it working.

Also, the PowerCLI has been updated, and can be found here. There are 68 new CMDLETS, which Alan Renouf does a great job of explaining. I’m especially looking forward to trying out Get\Set-CustomAttribute (no more manipulation of the View object), Move-VMTemplate (no more converting templates to machines), and Get\Set-VMQuestion (for those times when the datastores run out of space for the REDO files necessitated by Non-Persistent disks).

I’m looking forward to investigating the new PowerCLI functionality, and I’m also looking forward to not needing to  manually customise the dozen or so Windows 7 guests I’m deploying next week!

Downloading this at the moment, although I don’t suspect I’ll have time to look at it for a while.

One of the reasons we were moving to vSphere was the ability to thin-provision (TP) our disks, which we’re hoping will allow us to increase the amount of machines that we can provision without needing to allocate more storage (currently 18 TB).  I found an article by Duncan Epping over at Yellow Bricks suggesting the use of Sysinternals SDelete utility before the conversion to TP.

Essentially, as deleted files are not zeroed in Windows, and because VMware looks at the raw disk when “deallocating” space during conversion to think provisioned disks; deleted data are not reclaimed.  Running SDelete in the Windows guest before converting the disk to thin provisioned format zeroes the deleted data and should allow the maximum amount of space to be reclaimed.

While I don’t doubt that this is all correct, I wasn’t sure how much extra space it would allow us to reclaim. The majority of our guests are relatively small windows clients, almost all of which have non-persistent hard drives; of course – once they’ve been made non-persistent, the drive is effectively frozen, and subsequent use won’t increase the amount of non-zeroed slack space.

What’s the best way to see whether this is worthwhile? Run an experiment of course!

Method

I took one of our standard Windows XP guests which had been migrated to the new vSphere infrastructure. It had a 10GB hard drive, currently persistent, but which has been – for the majority of it’s 9 month existence – non-persistent. I examined how much disk space it was using, this was the pre-TP “Control”. I then cloned it without customization. One of the clones was converted to TP during a Storage vMotion operation. The other had slack space zeroed using SDelete (this process took around 3 minutes). It was then converted to Thin Provisioned disk format using Storage vMotion in the same way as the first machine.

Results

Here’s what happened

Normal (Thick) Disk

• Provisioned Storage: 10.50 GB
• Not-shared Storage: 10.00 GB
• Used Storage: 10.00GB

Converted to Thin Provisioned

• Provisioned Storage: 10.50 GB
• Not-shared Storage: 5.05 GB
• Used Storage: 5.05 GB

Converted to Thin Provisioned, after running SDelete

• Provisioned Storage: 10.50 GB
• Not-shared Storage: 4.21 GB
• Used Storage: 4.21 GB

Conclusion

Zeroing slack space on this typical machine saved me 0.84 GB (8.4%). For the minimal effort involved, I think this is worthwhile (I have about 500 more machines almost exactly the same as this).

The percentage of free space reclaimed would likely be higher on persistent machines, or larger machines which see frequent creation and deletion of files.

vAlarm is a Windows® based application which monitors alarms generated by VMware® vCenter.

The product is designed to be installed on an administrators PC, and provides automated monitoring of vCenter alarms without needing to be logged into a full VI Client console.

The software automatically communicates with a vCenter server on a user configurable schedule, and notifies any active alarms via a popup information bubble in the notification area of a users desktop.

The option to show details of all active alarms displays an information dialogue which lists individual alarms with detailed descriptions.

The software supports VMware vCenter 2.5 & 4.0.

It’s turned out to be quite handy, as it’s making me far more conscious of alarms. It might even encourage me to modify the default set of alarms – I’m generally not interested in guests going into the red because of CPU or memory due to the nature of the way they’re used, but I do need to know when hosts and datastores are running close to capacity.

The system tray application pops up a bubble, even when there are no alarms, which isn’t strictly necessary, and it might be nice to be able to collate notifications from more than one vCenter Server (I’m currently watching over two); but these are minor quibbles about a free product.

You can download vAlarm from XtraVirt (free registration required).