Components (deployment on Linux)
A SQL Server application deployed on Linux with Launch Wizard includes the following components:
-
A virtual private cloud (VPC) configured with public and private subnets across three Availability Zones. A public subnet is a subnet whose traffic is routed to an internet gateway. If a subnet does not have a route to the internet gateway, then it is a private subnet. The VPC provides the network infrastructure for your SQL Server deployment.
-
An internet gateway to provide access to the internet.
-
In the public subnets, network address translation (NAT) for outbound internet access. If you are deploying in your preexisting VPC, Launch Wizard uses the existing NAT gateway in your VPC. For more information about NAT gateways, see NAT Gateways.
-
Two of the private subnets each run a SQL Server replica node. One acts as the primary node, and the other as secondary node. The third private subnet is used to run the configuration replica. Launch Wizard deployments on Linux use Pacemaker
as the cluster resource manager. Pacemaker differs from Windows Server Failover Cluster (WSFC), which is used for Windows deployments, in terms of how it handles quorum. For Always On availability groups (AG) on Linux, arbitration happens in SQL Server where the metadata is stored. This is where the configuration-only replica is relevant. In order to maintain quorum and enable automatic failovers, Launch Wizard sets up a third node that acts as the configuration-only replica. -
Security groups to ensure the secure flow of traffic between the instances deployed in the VPC. For more information, see Security Groups for Your VPC.
The high-level architecture of a SQL Server high availability solution on Linux is
similar to the architecture for deployment on Windows. The main differences are the
low-level components and technologies. The architecture for Linux deployments provides
redundant databases and a configuration-only replica node to verify that a quorum can
vote for the node to be promoted to the controlling resource. The default architecture
mirrors an on-premises architecture of two SQL Server instances spanning two subnets
placed in two different Availability Zones. For more information about SQL Server Always
On Availability Groups (AG), see Overview of Always On Availability Groups (SQL Server)
