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TencentDB for MySQL
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    Selection Guide

    Last updated: 2023-12-27 10:58:01
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      Before purchasing a TencentDB for MySQL instance, it is important to learn about the features of different instances so that you can select one that meets your business requirements.

      Instance Information

      Prior to purchasing a TencentDB for MySQL instance, you must consider factors such as cost, performance, workload, and usage scenarios, so that you can select a suitable instance with optimal costeffectiveness. Since the database storage engine, instance architecture, storage type, and resource isolation policy are intricately intertwined and are mutually impacted, you may be confused when selecting an instance. This document briefly introduces these components to assist you in selecting an appropriate instance.

      1. Database Storage Engine

      A storage engine refers to the type of tables. The storage engine of database determines the manner in which tables are stored in a computer.
      InnoDB: The most frequently used OLTP storage engine, uses multi-version concurrency control (MVCC) and row-level locking technologies, offering high performance and reliable processing capabilities. In comparison to other MySQL storage engines, InnoDB offers functions including data foreign key and rollback, ensuring better data integrity. It also provides higher-level query functionalities. InnoDB kernel has been optimized a lot by Tencent Cloud and therefore has great performance advantages and is extensively applied in scenarios that involve high concurrency and require high performance.
      RocksDB: A popular high-performance persistent key-value (KV) storage based on which Tencent's TXSQL team develops TXRocks, a transactional storage engine. TXRocks, benefitting from the LSM Tree storage structure of RocksDB, has significantly reduced the waste caused by InnoDB's half-full page and fragmentation mechanisms, and utilized compact format storage. In this way, compared with InnoDB, TXRocks provides similar performance with half the storage space. It's more suitable for business scenarios that involve a large volume of data and require high read and write performance.

      2. Instance Architecture

      CDB MySQL supports three types of instance architectures: single-node, two-node, and three-node.
      
      Architecture
      Description
      Applicable Scenarios
      Single-Node
      Supported versions: MySQL 5.7 and 8.0.
      Node: Single Node.
      Personal learning, micro-websites, non-core small-scale enterprise systems, and the development and testing environments of large and medium-sized corporations.
      Two-Node
      Supported versions: MySQL 5.6, 5.7, and 8.0.
      Nodes: One Primary and One Standby.
      Primary-Standby Replication Mode: Asynchronous (default) and Semi-Synchronous
      Gaming, internet, IoT, retailing e-commerce, logistics, insurance, and securities, etc.
      Three-Node
      Supported versions: MySQL 5.6, 5.7, and 8.0.
      Nodes: One Primary and Two Standbys.
      Primary-Standby Replication Mode: Asynchronous (default), Strong-synchronous, and Semi-Synchronous
      Gaming, internet, IoT, retailing e-commerce, logistics, insurance, and securities, etc.

      3. Storage Classification

      The underlying storage of TencentDB for MySQL accommodates Local SSD, SSD CBS and Enhanced SSD CBS.
      Performance Metrics
      Enhanced SSD CBS
      SSD CBS
      Local SSD
      Maximum Capacity per Disk (GB)
      30000
      30000
      12,000
      Maximum IOPS per Disk
      Reaches 100,000 with additional performance included
      26000
      150000
      Calculation Formula of Random IOPS
      Baseline Performance: Random IOPS = min{1800 + Capacity (GiB) 50, 50000} Extra Performance: Maximum IOPS = min{Extra Performance Value 128, 50000} For more details, please refer to Enhanced SSD CBS Performance Description
      Random IOPS = min{1800 + Capacity (GiB) * 30, 26,000}
      IOPS is relevant to the instance specifications. For details, see Instance Specification.
      Maximum Throughput per Disk (MB/s)
      Reaches 1,000 with additional performance
      260
      -
      Throughput Calculation Formula (MB/s)
      Baseline Performance: Throughput = min{120 + Capacity (GiB) 0.5, 350} Additional Performance: Throughput = min{Additional Performance Value 1, 650} For details, please refer to Enhanced SSD CBS Performance Description.
      Throughput = min{120 + Capacity (GiB) * 0.2, 260}
      -
      One-Way Random Read/Write Latency (ms)
      0.2 - 1
      0.5 - 3
      Microsecond-level

      4. Resource Isolation Policy

      The resource isolation policies of CDB, including basic, general, and dedicated.
      Resource Isolation Policy
      Description
      Basic Type
      Only single-node instances support the basic isolation policy (formerly basic edition), where there is a separation between computing and storage, with the underlying layer using cloud disk storage.
      General Type
      An instance exclusively utilizes allocated memory and disk resources while sharing CPU resources with other general instances on the same physical machine.
      Benefit from resource sharing, bringing higher cost-effectiveness and minor CPU resource reutilization.
      The disk capacity is not tied to the CPU and memory, allowing for flexible matching.
      Dedicated Type
      An instance has dedicated CPU (with core binding), memory, and disk resources. It promises long-term performance stability and remains unaffected by the behavior of other instances on the physical machine.
      The peak configuration of the dedicated type is to occupy a physical machine alone, taking full control over all its resources.

      Product Selection

      You can follow the following steps to select an instance:
      1. Selecting Database Storage Engine If full transaction support and superior read-write concurrency are required, we recommend selecting InnoDB. If you want to cut down on storage costs, RocksDB would be the preferable choice. It provides comparable performance to InnoDB with only 50% or even less of the storage space.
      2. Selecting Instance Architecture Generally, a two-node architecture employing a classic primary-standby high-availability architecture is recommended. It is appropriate for industries like Internet, IoT, retailing e-commerce, logistics, gaming, or medium to large corporations. If your operations demand a financial-grade reliability, security, high availability, and disaster recovery abilities typical for industries such as finance, securities, insurance, or core database of large corporations, we recommend a three-node architecture. For personal learning, miniature websites, non-core small-scale enterprise systems, or the development and testing environments of large and medium-sized corporations, a single-node architecture would be a better choice.
      3. Selecting Storage Type The current options for storage type include local SSD disks for instances using a two-node or three-node architecture. The options for single-node architecture instances are SSD CBS and advanced SSD CBS. The cloud disk architecture single-node instances, based on a cloud-native architecture, are suitable for testing, development, personal learning and other scenarios. They support up to 30 TB storage space. The storage size has an impact on IOPS. For the performance metrics of different storage types, please refer to Storage Type.
      4. Selecting Resource Isolation Policy and Instance Specifications Single-node architecture supports basic isolation policy, and two-node and three-node architectures support both general and dedicated isolation policies. Instance specifications include parameters such as vCPU, memory, maximum IOPS, and maximum storage capacity. You can select based on your business requirements.
      Note：
      For details about all available models and selection options, please see Purchase Methods.

      Related Documents

      Architecture Overview
      Resource Isolation Policy
      Database Instance Type
      Database Instance Replication
      Database Instance Specifications
      
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