What Is GaussDB(DWS)?

GaussDB(DWS) is an online analytical processing (OLAP) database that runs on the Huawei Cloud infrastructure to provide scalable, fully-managed, and out-of-the-box analytic database service, freeing you from complex database management and monitoring. It is a native cloud service based on the converged data warehouse GaussDB, and is fully compatible with the standard ANSI/ISO SQL92, SQL 99, and SQL 2003, as well as the PostgreSQL and Oracle ecosystems. GaussDB(DWS) provides competitive solutions for PB-scale big data analysis in various industries.

GaussDB(DWS) comes in three types: standard data warehouse, stream data warehouse, and hybrid data warehouse, helping you build a data warehouse leading in the industry in terms of enterprise-level kernels, real-time analysis, collaborative computing, convergent analysis, and cloud native. For details, see Data Warehouse Types.

GaussDB(DWS) is widely used in domains such as finance, Internet of Vehicles (IoV), government and enterprise, e-commerce, energy, and telecom. It has been listed in the Gartner Magic Quadrant for Data Management Solutions for Analytics for two consecutive years. Unlike conventional data warehouses, GaussDB(DWS) is more cost-effective and has large-scale scalability and enterprise-level reliability.

This chapter describes the GaussDB(DWS) architecture and cluster logical architecture.

Architecture
Logical Cluster Architecture

Architecture

GaussDB(DWS) employs the shared-nothing architecture and the massively parallel processing (MPP) engine, and consists of numerous independent logical nodes that do not share the system resources such as CPUs, memory, and storage. In such a system architecture, service data is separately stored on numerous nodes. Data analysis tasks are executed in parallel on the nodes where data is stored. The massively parallel data processing significantly improves response speed.

Figure 1 Architecture
Click to enlarge

Application layer
Data loading tools, extract, transform, and load (ETL) tools, business intelligence (BI) tools, as well as data mining and analysis tools, can be integrated with GaussDB(DWS) through standard APIs. GaussDB(DWS) is compatible with the PostgreSQL ecosystem, and the SQL syntax is compatible with Oracle, MySQL, and Teradata. Applications can be smoothly migrated to GaussDB(DWS) with few changes.
API
Applications can connect to GaussDB(DWS) through the standard Java Database Connectivity (JDBC) 4.0 and Open Database Connectivity (ODBC) 3.5.
GaussDB(DWS) (MPP cluster)
A GaussDB(DWS) cluster contains nodes of the same flavor in the same subnet. These nodes jointly provide services. Datanodes (DNs) in a cluster store data on disks. Coordinators (CNs) receive access requests from applications and return the execution results to clients. In addition, a CN splits and distributes tasks to the DNs for parallel processing.
Automatic data backup
Cluster snapshots can be automatically backed up to the EB-level Object Storage Service (OBS), which facilitates periodic backup of the cluster during off-peak hours, ensuring data recovery after a cluster exception occurs.

A snapshot is a complete backup of GaussDB(DWS) at a specific time point, including the configuration data and service data of a cluster.
Tool chain
The parallel data loading tool General Data Service (GDS), SQL syntax migration tool Database Schema Convertor (DSC), and SQL development tool Data Studio are provided. The cluster O&M can be monitored on a console.

Logical Cluster Architecture

Figure 2 shows the logical architecture of a GaussDB(DWS) cluster. For details about instances, see Table 1.

Figure 2 Logical cluster architecture
Click to enlarge

**Table 1** Cluster architecture description
Name	Function	Description
Cluster Manager (CM)	Cluster Manager. It manages and monitors the running status of functional units and physical resources in the distributed system, ensuring system stability.	The CM consists of CM Agent, OM Monitor, and CM Server. CM Agent monitors the running status of primary and standby GTMs, CNs, and primary and standby DNs on the host, and reports the status to CM Server. In addition, it executes the arbitration instruction delivered by CM Server. A CM Agent process runs on each host. OM Monitor monitors scheduled tasks of CM Agent and restarts CM Agent when CM Agent stops. If CM Agent cannot be restarted, the host cannot be used. In this case, manually rectify this fault. NOTE: CM Agent cannot be restarted probably because of insufficient system resources, which is not a common situation. CM Server checks whether the current system is normal according to the instance status reported by CM Agent. In the case of exceptions, CM Server delivers recovery commands to CM Agent. GaussDB(DWS) provides the primary/standby CM Server solution to ensure system HA. CM Agent connects to the primary CM Server. If the primary CM Server is faulty, the standby CM Server is promoted to primary to prevent a single point of failure (SPOF).
Global Transaction Manager (GTM)	Generates and maintains the globally unique information, such as the transaction ID, transaction snapshot, and timestamp.	The cluster includes only one pair of GTMs: one primary GTM and one standby GTM.
Workload Manager (WLM)	Workload Manager. It controls allocation of system resources to prevent service congestion and system crash resulting from excessive workload.	You do not need to specify names of hosts where WLMs are to be deployed, because the installation program automatically installs a WLM on each host.
Coordinator (CN)	A CN receives access requests from applications, and returns execution results to the client; splits tasks and allocates task fragments to different DNs for parallel processing.	CNs in a cluster have equivalent roles and return the same result for the same DML statement. Load balancers can be added between CNs and applications to ensure that CNs are transparent to applications. If a CN is faulty, the load balancer automatically connects the application to the other CN. For details, see Associating and Disassociating ELB. CNs need to connect to each other in the distributed transaction architecture. To reduce heavy load caused by excessive threads on GTMs, no more than 10 CNs should be configured in a cluster. GaussDB(DWS) handles the global resource load in a cluster using the Central Coordinator (CCN) for adaptive dynamic load management. When the cluster is started for the first time, the CM selects the CN with the smallest ID as the CCN. If the CCN is faulty, CM replaces it with a new one.
Datanode (DN)	A DN stores service data by column or row or in the hybrid mode, executes data query tasks, and returns execution results to CNs.	A cluster consists of multiple DNs and each DN stores part of data. If no HA solution is available for DNs, data cannot be accessed when a DN is faulty.
Storage	Functions as the server's local storage resources to store data permanently.	-

DNs in a cluster store data on disks. Figure 3 describes the objects on each DN and the relationships among them logically.

A database manages various data objects and is isolated from other databases.
A datafile segment stores data in only one table. A table containing more than 1 GB of data is stored in multiple data file segments.
A table belongs only to one database.
A block is the basic unit of database management, with a default size of 8 KB.

Data can be distributed in replication, round-robin, or hash mode. You can specify the distribution mode during table creation.

Figure 3 Logical database architecture