VMworld 2017: Virtualizing AD

Session: VIRT1374BU: Matt Liebowitz

AD Replication
-Update sequence number (USN) tracks updates and are globally unique
-InvocationID – Identifies DC’s instance in the AD database
-USN + InvocationID = Replicable transaction

Why Virtualize AD?
-Fully supported by Microsoft
-AD is friendly towards virtualization (low I/O, low resource)
-Physical DCs waste resources

Common objections to virtualizing DCs
-Fear of stolen vmdk
-Privilege escalation – VC admins do not need to be domain admins and vice versa
-Must keep xx role physical – no technical or support reason. Myth
-Timekeeping is hard in VMs

Time Sync
-VM guest will get time re-set with vMotion and resuming from suspend. If there’s a ESXi host with bad time/date, it can cause weird “random” problems when DRS moves DCs around.
-There’s a set of ~8 advanced VMX settings to totally disable time sync from guest to ESXi host. Recommended for AD servers. See screenshot below.

Virtual machine security and Encryption
-vSphere supports VMDK encryption
-Virtualization based security – WS2016 feature – supported in future vSphere version

Best Practices

Domain Controller Sizing
USN Rollback
Happens when a DC is sent back into time (e.g. snapshot rollback)
-DCs can get orphaned if this happens since replication is broken
-If this happens, it’s a support call to MS and a very long, long process to fix it

VM Generation ID
-A way for the hypervisor to expose a 128-bit generation ID to the VM guest
-Need vSphere 5.0 U2 or later
-Active Directory tracks this number and prevents USN rollback
-Can be used for safety and VM cloning

Domain Controller Cloning
-Microsoft has an established process to do this, using hypervisor snapshots.
-Do NOT hot clone your DCs! Totally unsupported and will cause a huge mess.

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