AlwaysOn HADR

Question

Can you please suggest if it is feasible to create a SQL 2017 3 node (2 nodes in same DC and 1 in different DC)HADR for Alwayson for say 40 high performing databases :

1. If we have a sync replication for alwayson for the 2 Instances in same DC , I understand there will be latency due to sync replication and will impact performance vs async however with async we will not be having automatic failover without data loss.
2. Is it recommended to use alwayson for 40 or so high performing databases or is a MS Cluster more preferable.

Answer 1

Hi @Vishu ,

It depends on your requirements and need. Suggest you reading below links to get some comparison about AG and FCI, hope this could help you.

Should you choose a SQL Server Failover Cluster Instance or an Availability Group?
AlwaysOn AG versus FCI

>however in our case performance was the main criteria and hence the post.

There are many things will affect SQL Server performance, such CPU, network traffic etc. It’s hard to make a decision depend on performance.

---

If the response is helpful, please click "Accept Answer" and upvote it, as this could help other community members looking for similar queries.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

There is no simple answer to the question, because it is all a lot "it depends".

With an AG, you have different disks, you are protected against disk failures. With clusters, disks are shared, so there is no protection.

Then again, if both nodes in the AG are on the same SAN and the SAN breaks down, you are not better off.

An AG can give you a readable secondary. But that can be achieved by other means; log shipping or Transactional Replication.

And the list goes on.

You will first need to find out what your actual requirements are. Both with regards to performance and RPO/RTO.

Answer 3

Thanks for the elaborate information, however in our case performance was the main criteria and hence the post.

Thanks