Generally it is preferred to run exchange server on physical server due to performance reasons. It is possible to run virtualised exchange server roles in virtual environment. Virtualization platforms do provide features like server consolidation, quick provisioning, scalability, flexibility, business continuity and so on. Below is the conceptual representation of Exchange Server as VM on VMware vSphere platform.
However, running Exchange server in a virtual machine requires few additional measures to be taken into consideration.
- All Exchange server roles are supported in a virtual machine.
- Exchange server resource requirements for CPU and memory are same in virtualised environment to that of Physical server.
- Recommended Supported Processor Sockets is up to 2
- Intel processor that supports Intel 64 architecture (formerly known as Intel EM64T)
- AMD processor that supports the AMD64 platform
- Intel Itanium IA64 processors are not supported
- Mailbox role: 128GB minimum recommended
- Exchange Server 2019 supports up to 256 GB
- Do not use dynamic memory as Exchange server does not get full control of memory which leads to less performance
- Do not allocate vCPU to virtual machines at a ratio higher than two virtual processors per processor core i.e. 2:1 although recommended ratio is of 1 vCPU per Physical core i.e. 1:1.
- Dynamically expanding virtual disks is not supported due to performance reasons
- No spindle sharing. Storage used by Exchange should be hosted in disk spindles that are separate from the storage that’s hosting the guest virtual machine’s operating system.
- Snapshots are not supported as snapshot is done on virtual machine so it is not application aware.
- Ensure that additional 15 GB disk pace at least is allocated on top of the actual allocation size of disk. This is done due to paging requirements.
- Page file size is set to 25% of installed memory (recommended).
- Pass-through storage and iSCSI storage are both supported. For iSCSI storage which is a network based storage, use Jumbo frames.
- Virtual machine high availability that is provided by virtualisation environment can be used with Exchange server 2019 and it is supported even if DAG is enabled with few considerations as below.
- All migration between hosts must be an online migration or cold migration (Powered off VM migration). The virtual machines must not save and then restore state when migrated between hosts as in suspended state migration.
- If a virtual machine or host fails, the virtual machine must be restarted on an alternate host with a full boot process.