SQL 2019 Enterprise Cluster setup

Copper Contributor

Hey Guys, 

I'm in the process of setting up Always on HA cluster on SQL 2019 Enterprise on virtual environment.

Cluster will include SQL server instance on two separate Virtual machines with High availability groups - Synchronous replication

- Secondary - "Readable Secondary -NO" ?


Please help me clarify if;


a. Microsoft licensing allows having two SQL instances on two separate VM's with one license?

b. if yes, should the other node be Read-Only & Synchronous replication?

c. If yes, how will it help incase of DR or if downtime is required on Primary node?

d. If (b) is no, and both nodes have writable copy how does license taken into count?



1 Reply
Only one node (primary) is writable.
The secondary is either readable or not readable.
If secondary is readable and you use it to shift some load from primary (some applications use ApplicationIntent=ReadOnly; in connection strings) - you need the second license.

Asynchronous / Synchronous affects possible data loss during failover; it is not relevant to licensing.
Synchronous-commit mode emphasizes high availability over performance, at the cost of increased transaction latency. Under synchronous-commit mode, transactions wait to send the transaction confirmation to the client until the secondary replica has hardened the log to disk.