How Amazon EC2 High Availability for SQL Server works - Microsoft SQL Server on Amazon EC2
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How Amazon EC2 High Availability for SQL Server works

Upon registration, Amazon EC2 High Availability for SQL Server (SQL HA) automatically monitors your Amazon EC2 instances running Windows SQL Server License Included AMIs and classifies them as either active or standby based on their current role in your SQL Server deployment. For High Availability configurations containing an active SQL Server instance, one standby failover instance in the same cluster may receive a SQL Server licensing fee waiver, meaning you pay only the Windows Server licensing fee. You can monitor your current SQL HA status through the Amazon EC2 console, which displays the latest records of which instances are receiving license savings and historical status changes.

SQL HA continuously monitors your enabled SQL Server instances to determine their active or standby status. Using Amazon Systems Manager (SSM) commands, it collects metadata from your SQL Server installations and applies classification logic to identify which instances are actively serving traffic and which are functioning as standby failover nodes.

Standby instances are billed as Windows instances rather than Windows SQL Server instances, providing license cost savings. Billing changes take effect when an SQL HA standby detection enabled instance is classified as standby and eligible for the benefit, with no manual intervention required. This classification adapts to changes in your environment, such as failover events where a standby instance becomes active. The system detects these transitions and updates billing accordingly.