Figure 12.11 Viewing the fault domain and update domains for an availability set
This information can also be seen with PowerShell:
PS C:> $AS.VirtualMachinesReferences | ForEach { $VMResource =(Get‐
AzureRmResource -Id $_.id); $VM= Get-AzureRMVM -Name $VMResource.Name –
ResourceGroup $VMResource.ResourceGroupName -Status;
[PSCustomObject]@{"Name"=$VM.Name;
"FaultDomain"=$VM.PlatformFaultDomain;"UpdateDomain"=$VM.PlatformUpdateDom
ain;}}
Name FaultDomain UpdateDomain
WebSrv1 0 0
WebSrv2 1 1
WebSrv3 2 2
WebSrv4 0 3
With Azure Resource Manager, a VM can be added to an availability set only at the
time of creation. If you need to change the availability set membership of a VM, you
would need to delete and re-create it. Note that the storage of a VM does not have to
be deleted, which is the actual state of the OS. Instead, a VM is deleted, but its storage
is kept. A new VM is created using the existing VHDs, which essentially re-creates the
old VM. It’s important to make sure that availability sets contain only virtual
machines that are performing exactly the same function. If you mix the functions of
virtual machines into a single availability set, the virtual machines performing the
same function could end up in the same fault domain, which would be a very bad