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What Is DDS?

Updated at: Mar 13, 2020 GMT+08:00

Document Database Service (DDS) is compatible with MongoDB and is secure, highly available, reliable, scalable, and easy to use. It provides DB instance creation, scaling, redundancy, backup, restoration, monitoring, and alarm reporting functions with just a few clicks on the DDS console.

Why DDS?

  • Automatically sets up three-node replica set architecture. DDS supports fast deployment, high availability (HA) data storage, data redundancy, and failover support.
  • Provides sharded cluster instances consisting of shard, mongos, and config, enabling you to easily enhance read and write performance and build a distributed DDS database system.
  • Provides database backup and restoration functions in one-click mode. Allows you to back up and restore the database on the console.
  • Provides performance metrics and sets alarms on any of the metrics to send you notification. You can quickly monitor instance status and identify issues at a glance.

For more details, see Comparison Between DDS and On-Premises Database and Typical Application Scenarios.

Compatible DB Engines and Versions

For details about the compatible DB engines and versions, see Database Engine and Version.

Product Architecture

DDS supports multiple deployment modes to meet different service scenarios.

Table 1 Architecture description

Instance Architecture



The DDS cluster consists of three types of nodes: mongos, shard, and config. The architecture of these nodes varies. You can configure the number of mongos and shard nodes as required. mongos uses a single-node architecture, and shard and config use a three-node replica set architecture. For details, see Cluster Architecture.

Replica set

In the replica set instance, there are three types of nodes: primary, secondary, and hidden. You can operate the primary and secondary nodes directly. A replica set instance supports DR switchover and high availability. It is transparent to your applications. For details, see Replica Set Architecture.

Deployment Suggestions

It is recommended that you deploy DDS by considering the following factors:

  • Region and Availability Zone (AZ) describe the location of DDS DB instances. Once the DB instance is successfully created, the region cannot be changed. You can select regions and AZs based on the geographical locations of users, product prices, DR capabilities, and network latency. For more information, see Region and AZ.
  • Network planning: You are advised to create the DDS DB instances in the Virtual Private Network (VPC) and subnet where the Elastic Cloud Servers (ECSs) are deployed.
  • Data security: DDS provides comprehensive security assurance for the data security that you may concern. You can deploy DB instances in multiple AZs and use audit logs, isolated networks, security groups, and data encryption to ensure data security.

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