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Product Architecture

Context

DWS is an MPP system with the shared-nothing architecture. It consists of multiple independent logical nodes that do not share system resources, such as the CPU, memory, and storage units. In this system architecture, service data is separately stored on numerous nodes. Data analysis task is executed at the location nearest the data. Coordinated control modules enable massively parallel data processing and quick response to data processing.

DWS Software Architecture

DWS is a distributed parallel database cluster with the shared-nothing architecture, as shown in Figure 1.

Figure 1 DWS product architecture

  

Figure 2 shows the logical architecture of DWS. For details about the instance, see Table 1.

Figure 2 Logical architecture
Table 1 Architecture description

Name

Description

GTM

Global Transaction Manager: generates and maintains the global unique information, such as the global transaction ID, transaction snapshot, and timestamp.

WLM

Workload Manager: controls allocation of system resources to prevent service congestion and system crash resulting from excessive workload.

CN

Coordinator Node: receives access requests from applications, and returns execution results to the client. The CN breaks down tasks and allocates task fragments to different DNs for parallel processing.

DN

Data Node: stores service data by column or row or in the hybrid mode, executes data query tasks, and returns execution results to CNs.

Storage

Functions as the server's local storage resources to store data permanently.

DNs in a cluster store data on disks. Figure 3 logically describes the objects on each DN and the relationship among them. Other related concepts are as follows:

  • Database: A database manages various data objects and is isolated from each other.
  • Datafile Segment: A data file, each of which stores data of only one table. A table containing more than 1 GB of data is stored in multiple datafile segments.
  • Table: One table belongs to only one database.
  • Block: The basic unit of database management. Its default size is 8 KB.

Data can be distributed in REPLICATION, ROUNDROBIN, or HASH mode. You can set it while creating a table. ROUNDRONIN only applies to foreign tables.

Figure 3 Database logical architecture