Exchange 2019 Preferred Architecture (Preferred Architecture)

Microsoft has published details of the preferred architecture for Exchange 2019. This is a whole series of best practices for an Exchange 2019 environment.

The article can be found here:

• Exchange 2019 preferred architecture

Here is a brief summary of the most important points and a few small comments on my part.

Namespaces

The best practice provides for 4 DNS names for an Exchange 2019 environment. The names separate the protocols from each other:

• Autodiscover: autodiscover.contoso.com
• HTTP clients: mail.domain.de
• IMAP clients: imap.domain.de
• SMTP clients: smtp.domain.de

All DNS names must be present on the certificate. In this case, the certificate would therefore have to contain 4 DNS names. If IMAP is not used and an upstream SPAM filter is used, the names for IMAP and SMTP are omitted, so the certificate only needs to contain 2 DNS names (mail.domain.de and autodiscover.domain.de).

Here is an example of the recommended architecture with two data centers and one DAG:

Source: Exchange 2019 preferred architecture

In this case, the DAG is spanned across 2 data centers. In each data center there is a load balancer that distributes the load to the local Exchange servers. In this case, the clients are distributed to the respective data centers via DNS Round Robin or GeoDNS.

Of course, Exchange 2019 can still be operated in just one data center, even without a DAG and load balancer.

Server hardware

Virtualization is supported, but Microsoft recommends installing Exchange 2019 with the operating system directly on the hardware. If a DAG with several servers is used across several data centers, it makes little sense to use a virtualization layer, in which case there is hardly any added value. However, individual servers can still be operated on Hyper-V or VMware.

The hardware recommendation is as follows:

• 2U server with space for 12 or more drives
• 2 processors with up to 48 CPU cores
• Up to 256 GB RAM (128 GB RAM minimum. Yes, less will work, but it is not recommended)
• RAID controller with write cache (BBU, battery-backed write cache)
• The RAID controller must support the simultaneous operation of HDDs and SSDs

Storage

Best practice provides for a RAID1 for the operating system, Exchange installation, log files (not database logs) and transport database. A JBOD of SAS HDDs with 7200rpm is recommended for the databases and transaction logs.

If the new MCDB (Metacache Database) feature is to be used, SSDs must also be installed in the servers. The following recommendations apply here:

• 1 SSD should be installed for every 3 HDDs (standard SAS SSDs, mixed used)
• 5-10% of the capacity of the HDDs should be available as SSD capacity
• No RAID required for the SSDs (only serve as "read cache")

The following figure shows a corresponding HDD/SSD configuration:

• 2 HDDs for the operating system and Exchange 2019
• 12 HDDs for Exchange databases and logs
• 1 HDD as DAG AutoReseed Spare Disk
• 4 SSDs for the metacache database

Source: Exchange 2019 preferred architecture

File system

NTFS is still used for the operating system and the Exchange installation. ReFS is recommended for the databases and MCDB (with the Integrity feature switched off).

DAG

A single network card is recommended for the DAG (no teaming). Depending on the design, a third page is required for the DAG-Witness. If there are only two data centers, the Witness can now also be stored in Azure. Alternatively, a local Witness can still be used, in which case the Witness and PAM should be located in the same data center.

Comment / Opinion

Microsoft is positioning Exchange 2019 as a pure enterprise product. However, it is still possible to operate Exchange 2019 in smaller environments, but this requires a volume license agreement with Microsoft. However, the path is already quite clear here: Cloud.

The times when Exchange was delivered with an SBS server are over and will not return. However, SBS customers in particular can benefit from Office 365. Instead of running a dusty server in the storeroom, they can use Office 365 and thus use even more services than just Exchange. Of course, many small customers will not be able to do completely without a local server, but it is inevitable that there will be no local Exchange server for small and medium-sized companies. Perhaps more Domino servers will be installed again :-)