Instance Type | Introduction | Usage Instructions | |
Single-node instance | Single-node (formerly Basic Edition) instance | It employs a single-node database deployment architecture, contains only one node, and offers a lower usage cost. It features a decoupled compute and storage architecture, with underlying data stored on cloud disks using a triple-replica mechanism. The basic edition node is deployed on a CVM, delivering better database performance compared to self-built solutions. The storage medium uses high-performance cloud disks, which are widely applicable to various I/O scenarios and deliver stable performance. | Suitable for personal learning, ISV software for small and medium-sized enterprises, Web applications, non-core small-scale enterprise systems, and testing environments. The single-node architecture consists of a single node and lacks primary/secondary automatic failover capability. Fault recovery typically relies on instance rebuild and data restoration, and the recovery time may be longer than that of high-availability architectures. |
Primary/Replica instance | Two-node (formerly HA Edition/Cluster Edition) instance with a one-primary-one-replica architecture. | Supports SQL Server 2012/2014/2016 Enterprise and SQL Server 2012/2014/2016 Standard editions. It consists of a one-primary-one-mirror SQL Server database. The classic one-primary-one-secondary architecture is adopted, with the specifications of each node in the primary/replica instances being consistent. The primary and secondary nodes are deployed cross-rack or cross-AZ. Each database corresponds to a set of monitoring agents, which perform real-time monitoring of the database through heartbeat. Cross-AZ high availability is supported. The primary AZ and secondary AZ should be selected to be in different AZs. COS: Provides data disaster recovery services and cold backup data. Tencent Cloud management cluster: Consists of independently deployed decision scheduling clusters and configuration clusters, serving as the management and scheduling center for the cluster. It primarily manages the normal operation of database node groups, access gateway clusters, and COS. | The standby instance enhances the reliability of the instance. During the creation of a primary instance, a standby instance is created synchronously. Once the standby instance is successfully created, it is not visible to users. When the primary node fails, a switch between primary and secondary occurs automatically. The database client experiences a brief interruption and must support reconnection. Data replication between SQL Server primary/secondary nodes is asynchronous by default. Similarly, replication between the primary instance and read-only instances is also asynchronous by default. |
| | SQL Server 2017/2019/2022/2025 Enterprise edition adopts the Always On architecture (including one-primary-one-secondary), supports adding up to five read-only instances, builds a cluster mode, and offers higher availability, reliability, and scalability. The primary and secondary nodes are deployed cross-rack or cross-AZ. Each database corresponds to a set of monitoring agents, which perform real-time monitoring of the database through heartbeat. | Suitable for industry applications such as gaming, healthcare, pharmaceuticals, internet, IoT, retail, e-commerce, logistics, insurance, securities, media, technical services, and automotive. |
| Multi-node instance with a one-primary-multiple-replica architecture (2 to 5 replica databases can be selected) | Supports SQL Server 2017/2019/2022/2025 Enterprise edition and adopts a one-primary-multiple-secondary architecture. Replica nodes provide disaster recovery. After enabling replica node read-only, they can also provide a replica node read-only address for read capability. Standby databases can be deployed across different AZs, which helps reduce the impact of data center-level failures on business. | Suitable for business systems with high availability requirements, such as the financial industry and the e-commerce industry; suitable for business scenarios involving large-scale data processing, such as big data analysis and log processing. |
RO instance | Read-only instances | A single-node (without standby) instance that can support read requests. A read-only instance cannot exist independently. Each read-only instance belongs to an RO group and must be bound to a primary instance (two-node) for use. An RO group is a read-only instance group with CLB functionality. | A read-only instance is a single-node edition. After a physical server failure or database replication exception occurs, the instance requires a relatively long time to be rebuilt and recovered, depending on the data volume. For business scenarios that heavily rely on read operations, it is recommended to create multiple read-only instances to distribute the database read load. |
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