Forum Discussion

peanut123's avatar
peanut123
Occasional Reader
Mar 16, 2026

How to add a new domain controller to an existing Active Directory domain?

The specific situation is as follows:

  1. The company has one forest and domain, and two Active Directory (AD) servers. These two servers communicate and synchronize data.
  2. One server is deployed in the local data center, and the other is deployed on Azure Cloud.
  3. The forest and domain functional levels are both Windows Server 2008 R2. Both servers are running Windows Server 2016 Standard.
  4. Because there are computers running Windows XP and Windows 7 in the domain, upgrading the forest and domain functional levels is not possible. Windows Server 2008 R2 must be retained.
  5. The company now needs to add a new AD server on Huawei Cloud and join it to the company's forest and domain.

The main questions are:

  1. How do I determine which operating system the new server should run? Excluding Windows Server 2016.

How should I choose between Windows Server 2019, 2022, and 2025?

  1. How do I determine how to allocate CPU, memory, disk, and network resources during system deployment?
  2. How to determine which operating system is best suited for running a domain controller without conflicts or incompatibility?
  3. What preparations should be made before deploying a new server?
Active Directory
AzureAD
huawei cloud
windows server

1 Reply

  • gavinstrawbridge's avatar
    gavinstrawbridge
    Copper Contributor
    Mar 16, 2026

    Hi,

     

    This is what I would recommend:

     

    How do I determine which operating system the new server should run?

    Choose a Windows Server version that is supported as a domain controller with your current forest/domain functional level (2008 R2).

    How should I choose between Windows Server 2019, 2022, and 2025?

    Select Windows Server 2022 because it offers the best balance of stability, compatibility, and long-term support.

    How do I determine CPU, memory, disk, and network resources?

    Size the domain controller based on domain size and replication load, typically 2–4 vCPU, 8–16 GB RAM, ~100–200 GB disk, and stable network connectivity.

    How to determine which OS is best suited for running a domain controller without conflicts or incompatibility?

    Choose the newest Windows Server version officially supported by your current AD functional level and existing domain controllers.

    What preparations should be made before deploying a new server?

    Verify AD replication health, DNS functionality, SYSVOL replication (DFSR), network connectivity, and FSMO role status before promoting the server to a domain controller.