|By Tommy Patterson||
|January 25, 2013 11:00 AM EST||
Migrating traditional client/server applications to Windows Azure Virtual Machines is what Don Noonan does every day. The majority of these workloads use Active Directory Domain Services as their authentication provider, or in other words, classic Windows authentication. In this post Don walks us through the best practices high level architecture and the basic building blocks of creating a private forest within Windows Azure.
If Active directory is not available, you better be
As we all know, if AD is down so is your app. Imagine setting up a single domain controller responsible for both name resolution (DNS) and authentication. You just created another synonym for single-point-of-failure. At a minimum you should deploy two (2) domain controllers, and they should be created as part of an Availability Set. This will ensure that at least one (1) domain controller is always available for authentication and name resolution requests. If you’re considering saving a few bucks by deploying a single domain controller in non-production environments, let me save you a few more. The first call you get from development or QA will cost you at least 6 months of compute. Telling a dozen upset people on a conference call that you wanted to save the company $50/month will sound pretty bad…
A private forest for me? oh you shouldn’t have
There are currently two major scenarios for providing Windows authentication in Windows Azure Virtual Machines:
- Deploy a new private forest
- Extend an existing on-premise forest
In this blog we’ll cover deploying a new private forest. Here is a quick Visio of a classic 3-tier application (using Windows Azure features) to get us started:
As you can see, we have a management subnet that contains our domain controllers, as well as separate database and application “tiers”.
Stop Talking and Start Deploying
As with any new deployment to Windows Azure Virtual Machines, you will perform the following high-level steps:
- Create an affinity group (See Bob Hunt’s Article in the Series)
- Create a virtual network (See Bob Hunt’s Article in the Series)
- Create a storage account (See Kevin Remde’s Article in the Series)
- Create virtual machines (See Tommy Patterson’s Article in the Series)
While creating the virtual network, you will need to specify that the domain controllers will also be providing name resolution for all of the servers in your deployment. You can do this in the Windows Azure management portal as well as through the management web service. Here is how you do this via PowerShell:
Specifying custom DNS servers using PowerShell
Example command line:
Set-AzureVNetConfig –ConfigurationPath “C:\networkConfiguration.xml”
Contents of C:\networkConfiguration.xml:
<DnsServer name="skydc01" IPAddress="10.1.1.4" />
<DnsServer name="skydc02" IPAddress="10.1.1.5" />
<VirtualNetworkSite name="skyvn" AffinityGroup="skyag">
<DnsServerRef name="skydc01" />
<DnsServerRef name="skydc02" />
In the example above, the IP addresses used assume the domain controllers are the first virtual machines created on the Management subnet. Let’s make sure that’s true by creating them now:
Creating Highly Available Domain Controllers using PowerShell
Relevant excerpts from createService.ps1:
$instanceSize = 'Small'
$imageName = 'MSFT__Win2K8R2SP1-Datacenter-201210.01-en.us-30GB.vhd'
$subnetName = 'Management'
$availabilitySetName = 'skydc'
$password = '@skyDc01'
$vmName = 'skydc01'
$skydc01 = New-AzureVMConfig -Name $vmName -AvailabilitySetName $availabilitySetName -ImageName $imageName -InstanceSize $instanceSize |
Add-AzureProvisioningConfig -Windows -Password $password |
$password = '@skyDc02'
$vmName = 'skydc02'
$skydc02 = New-AzureVMConfig -Name $vmName -AvailabilitySetName $availabilitySetName -ImageName $imageName -InstanceSize $instanceSize |
Add-AzureProvisioningConfig -Windows -Password $password |
Once you’ve created the servers, you will need to make them domain controllers, also known as promotion.
Promoting a Server to a Domain Controller using DCPROMO or PowerShell
Depending on what operating system you have chosen, you can automate forest creation via command line. In the following examples, be sure to replace DOMAIN_HERE with the desired domain name, and replace passwords with those corresponding to temporary password you assigned to the local administrator account on the first (primary) server.
Windows Server 2008 R2 – Create a new forest using DCPROMO
Contents of C:\primaryDomainController.txt:
; New forest promotion
Windows Server 2012 – Create a new forest using PowerShell
Contents of C:\primaryDomainController.ps1:
-DatabasePath "C:\Windows\NTDS" `
-DomainMode "Win2012" `
-DomainName "[DOMAIN_HERE].com" `
-DomainNetbiosName "DOMAIN_HERE" `
-ForestMode "Win2012" `
-LogPath "C:\Windows\NTDS" `
-SysvolPath "C:\Windows\SYSVOL" `
Part of your homework will be to create the second domain controller in the new forest. There will need to be slight changes made to the answer files above.
Creating the rest of servers required by your application seems like the logical next step. However, there are a handful of important tasks I like to do prior to creating ANY additional virtual machines:
Create domain user accounts that will be used for future system administration.
Create containers for major objects such as server computer accounts.
Create core group policies for significant items such as:
- Remote Desktop Services – Enable Keep-Alives (article posted previously at Skylera)
- User Account Control
- Windows Firewall
- Windows Update
When creating a private forest, consider the amount of administrative overhead involved vs. level of isolation. For example, you may want to have a single forest for all pre-production environments so that you only need to perform user account tasks in one place. This is easy to do in Windows Azure.
Written by Don Noonan (Don's Blog at Skylera)
Edited by Tommy Patterson (Tommy's Blog on Virtuallycloud9.com)
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