Adding node to SQL 2008 cluster does not require SQL restart.

Chris Skorlinski
SQL Server Escalation Services

We had this question about SQL 2008 virtual cluster. 

Question:  Is it possible to add node in existing SQL Server 2008 or 2008 R2 Failover cluster instance without downtime (without stopping SQL Server or MSCS services)?

Answer: Absolutely! SQL Server 2008 was designed with rolling installation and upgrades in mind. To confirm:

1. I built a 2-node Windows 2008 R2 Cluster using Windows 2008 HyperV

2. I installed SQL 2008 R2 to the 1st node of the cluster

3. I started a long running SQL transaction

4. Next I installed SQL to the 2^nd node and selected to join the existing virtual SQL Server 2008

The transaction running on the 1^st node was never interrupted.