7.1.5 Document Database Service (DDS)

Question 1

What Is DDS?

Answer 1

Document Database Service (DDS) is a high-performance, highly availability MongoDB-compatible
database service that is scalable and secure. It provides one-click deployment, elastic capacity
expansion, disaster recovery, backup, restoration, monitoring, and alarm reporting.
• Each DDS cluster is an independent document database. A sharded cluster consists of a config node, and multiple mongos and shard nodes.
• Data read and write requests are forwarded by the mongos nodes, which read configuration settings from config, and then allocate the read and write requests to the shards, making it easy to cope with high concurrency scenarios. In addition, each config node, along with the shards in its cluster, is replicated in triplicate to ensure high availability.

Question 2

What are DDS Advantages?

Answer 2

1. 100% MongoDB
   compatibility
2. Reliable, available,
   and secure
3. Efficient O&M
4. 3 types of
   architectures
   • Fully compatible
   DDS is a document-oriented NoSQL database that is fully compatible with MongoDB.
   • Reliable, available, and secure
   ▫ The security system consists of VPCs, subnets, security groups, Anti-DDoS, and SSL, which collectively can defend against a wide range of attacks and keep your data secure. DDS supports audit logs, which can be stored for up to two years. DDS supports fine-grained permission control. The cluster and replica set support high availability. If the primary node is faulty, the secondary node quickly takes over services. The switchover process is unnoticeable to the applications.
   ▫ DDS supports both automated and manual backup. The maximum retention period for an automated backup is 732 days. A manual backup can be retained until you delete it.
   ▫ You can restore a DB instance from a backup file. Replica sets support point-in-time recovery at the instance, database, and table-level.
   • Efficient O&M
   ▫ DDS console is a visualized instance management platform. You can restart,
   back up, or restore an instance in just a few clicks.
   ▫ DDS monitors key performance metrics of DB instances and DB engines in real time, including the CPU usage, memory usage, storage space usage, command execution frequency, delete statement execution frequency, insert statement execution frequency, and the total number of active connections.

Question 3

What are the three types of nodes of a DDS Cluster?

Answer 3

1. Mongos
2. Config
3. Shard

Question 4

What is mongos? (from three types of DDS Cluster)

Answer 4

Each mongos node routes read
and write requests, providing a
unified interface for accessing DB
instances.

Question 5

What is config? (from three types of DDS Cluster)

Answer 5

A config node is deployed as a
replica set and stores instance
configuration data.

Question 6

What is shard? (from three types of DDS Cluster)

Answer 6

Shard nodes store user data.