Hot Add Memory on vSphere 4.1. Is it useful?

Since vSphere 4.1, you can Hot Add memory inside a VM depending on the OS type.

I’m not going into the details on how to add the memory as that is described in numerous posts on the internet.

 

Let’s assume we have a Windows Server 2008 R2 with 5 GB of memory and a x64 application consuming 10 GB of RAM (we use TestLimit64 from sysinternals in this example, but typically this application could be Exchange, SQL, …).  I know, it sounds awful (as a matter of fact, it is awful 🙂 ).

If we look in Task Manager, we can see the server has severe memory shortage:

Hot Remove a hard disk from a Virtual Machine on vSphere 4.1

Hot Adding hard disks has been around since the stone ages on VMware platforms.  As from vSphere 4.1, you can also Hot Remove a hard disk (VMDK and RDMs!) from a Virtual Machines.  This means that there is no downtime for the Virtual Machine and no reboot is necessary!

In my opinion this is a huge improvement and quite a benefit.

You have to be carefull however to remove/disable/uninstall/whatever the hard disk inside the VM first to make sure that the VM is not affected.

The remove operation is not a big deal for vSphere, but if your VM is still accessing that disk, things might get ugly inside the VM…  (just think of a physical Windows box and disappearing SAN connection 🙂 ).

Let’s see how to Hot Remove a hard disk for a Windows Server 2008 R2.  This method works from Windows 2000 and higher but the screenshots might differ.

How to Hard Kill a stuck VM with PowerCLI

Sometimes a VM is stuck and can’t be killed with vSphere Client (or from within the VM).

On ESX, you could login and perform the famous kill –9 <PID> to kill the VM.  Most people don’t realize that this functionality has been added to PowerCLI in version 4.1 Update 1.

First, connect directly to the ESX(i) host.

Connect-VIServer -Server <Hostname> -Credential $(Get-Credential -Credential root)

PowerCLI: Convert PortWorldWideName or NodeWorldWideName to hexadecimal format.

If you output one of the fields of $VMHost.Config.StorageDevice.MultipathInfo.Lun[x].Path[x].Transport, you will get the output in standard decimal numbers.

This is different from what is used in SAN environment where they mostly use XX:XX:XX:XX:XX:XX:XX:XX where XX is a hexadecimal number.

 

Use the following code to convert from the decimal format to the hexadecimal SAN format:

[String] $lstrWWNNHex = "{0:x}" -f $NodeWorldWideName
[String] $lstrWWNNHexFormatted = ""
For ($i=0;$i -lt 8;$i++)
{
    $lstrWWNNHexFormatted += "{0}:" -f $($lstrWWNNHex.SubString($i * 2, 2))
}
$lstrWWNNHexFormatted = $lstrWWNNHexFormatted.SubString(0, $lstrWWNNHexFormatted.Length - 1)

$NodeWorldWideName is the WWN generated by $VMHost.Config.StorageDevice.MultipathInfo.Lun[x].Path[x].Transport.NodeWorldWideName.  You can use the same for PortWorldWideName.

How to check if PowerCLI libraries are loaded in PowerShell/PowerGUI

If you write scripts in PowerShell or PowerGUI, it might be handy to check if the PowerCLI libraries are loaded.

Even though you have PowerCLI installed, this does not mean the objects are loaded in your PowerShell session.

In PowerGUI for example, you can check this by clicking File – PowerShell Libraries.