Apsara PolarDB is a next-generation relational database that is developed by Alibaba Cloud. PolarDB has three independent engines. This allows PolarDB to be fully compatible with MySQL and PostgreSQL, and allows PolarDB databases to be compatible with the Oracle syntax. Each PolarDB cluster supports a maximum storage space of 100 TB. You can add a maximum of 16 nodes to each PolarDB cluster. This makes PolarDB applicable in various scenarios.
PolarDB uses an architecture where computing is decoupled from storage. All the compute nodes of PolarDB clusters share the same physical storage. PolarDB allows you to upgrade or downgrade instance specifications within a few minutes, and to perform fault recovery within several seconds. PolarDB ensures global data consistency, and offers free services for data backup and disaster recovery. PolarDB incorporates the benefits of commercial databases and open source cloud databases. Commercial databases are stable and scalable and have high performance. Open source cloud databases are easy to use and feature rapid iteration. For example, the performance of PolarDB for MySQL is six times that of MySQL. However, the cost of a PolarDB for MySQL database is only 10% that of a commercial database.
- Cluster architecture where computing is decoupled from storage
PolarDB uses a cluster architecture. A PolarDB cluster consists of one writer node and multiple reader nodes. The write node serves as the primary node and the reader nodes that serve as read-only nodes. All the nodes share the same underlying physical storage by using the distributed file system: PolarFileSystem. The underlying physical storage is known as PolarStore.
- Read/write splitting
PolarDB uses PolarProxy to provide external services for the applications that are connected to cluster endpoints. The proxy forwards the requests from the applications to database nodes. You can use the proxy to implement authentication, data protection, and automatic read/write splitting. The proxy parses SQL statements, sends write requests to the primary node, and distributes read requests such as SELECT requests to read-only nodes for load balancing. The write requests include transaction, UPDATE, INSERT, DELETE, and data definition language (DDL) requests. The proxy allows applications to access PolarDB for MySQL in the same way as they access a single-node database.
- Large capacity
Each cluster supports a maximum storage space of 100 TB. You no longer need to purchase instances for database sharding due to the storage limit of a single host. This simplifies the development of applications and reduces the workload of operations and maintenance (O&M).
- High cost efficiency
- PolarDB decouples computing from storage. You are billed for the computing resources of each read-only node that you add to a PolarDB cluster. For traditional databases, you are billed for computing and storage resources in the same case.
- You do not need to manually configure the storage of a PolarDB cluster. The storage space is automatically changed based on the volume of the stored data. You need only to pay for the storage space that you use.
- Elastic scaling within several minutes
You can scale up a PolarDB cluster by using the shared storage and the architecture where computing is decoupled from storage.
- Read consistency
Log Sequence Numbers (LSNs) are applied to cluster endpoints. This ensures global consistency for read operations and avoids inconsistency that is caused by the replication delay between the primary node and read-only nodes.
- Millisecond-level delay in physical replication
PolarDB performs physical replication between the primary node and read-only nodes based on redo logs. The physical replication replaces the logical replication that is based on the binary logs and improves the efficiency and stability of replication. No delay occurs for PolarDB even if you perform DDL operations on a large table, such as adding indexes or fields.
- Unlocked backup
You can create a snapshot for a database of 2 TB in size within 60 seconds. During the backup process, the database is not locked. This minimizes the impact of the backup on your applications. You can back up the data in the database at any time based on your business requirements.
You can use the following methods to manage PolarDB clusters. For example, you can create clusters, databases, and accounts.
- Console: This method provides a visual web interface and simplifies management operations.
- CLI: You can use the command-line interface (CLI) to perform all the operations that are available in the console.
- SDK: You can use the software development kit (SDK) to perform all the operations that are available in the console.
- API: You can call API operations to perform all the operations that are available in the console.
After a PolarDB cluster is created, you can connect to the PolarDB cluster by using the following methods:
- DMS: You can connect to a PolarDB cluster by using Data Management System (DMS) and develop databases on the web interface of DMS. For more information, see Use DMS to connect to a cluster.
- Client: You can connect to a PolarDB cluster by using general database clients. For example, you can use MySQL-Front or pgAdmin to connect to a PolarDB cluster.
Before you purchase and use PolarDB , we recommend that you understand the following terms:
- Cluster: A cluster consists of a primary node and a maximum of 15 read-only nodes. PolarDB uses a cluster architecture.
- Region: A region is a physical area where a data center is deployed. In most cases, PolarDB clusters are deployed in the same region as Elastic Compute Service (ECS) instances to ensure optimal access performance.
- Zone: A zone is a physical area in a region. This area has an independent power supply and network. All the zones in a region provide the same services.
- Specification: A specification specifies the resources that are configured for each node, such as 2 CPU cores and 8 GB memory.
- ECS instances serve as cloud servers. If your PolarDB clusters are deployed in the same region as the ECS instances and you access the PolarDB clusters over an internal network, the PolarDB clusters provide optimal performance. In a typical service architecture, ECS instances are used in conjunction with PolarDB clusters.
- ApsaraDB for Redis is a database service that supports in-memory storage and persistent storage. You can combine ECS instances, PolarDB clusters, and ApsaraDB for Redis instances to handle a large number of read requests and reduce the response time.
- ApsaraDB for MongoDB: ApsaraDB for MongoDB provides stable, reliable, and scalable database services that comply with the MongoDB protocol. To meet diverse business demands, you can store structured data in PolarDB and unstructured data in ApsaraDB for MongoDB.
- DTS: You can use Data Transmission Service (DTS) to migrate on-premises databases to cloud-based PolarDB clusters.
- OSS: Object Storage Service (OSS) is a secure, cost-effective, and reliable cloud storage service that allows you to store large volumes of data.