This topic provides an overview of the storage types supported by ApsaraDB for RDS, including local SSDs, standard SSDs, and enhanced SSDs (ESSDs). ApsaraDB for RDS provides reliability, availability, and read/write performance for all of the above storage types based on Alibaba Cloud service level agreement (SLA) requirements.

Overview

You can use the following three storage types for various scenarios.

  • Local SSD (Recommended)

    A local SSD is a storage device in the server node where the database engine resides. With local SSDs, computing is closer to data to reduce the I/O latency.

  • Standard SSD

    A standard SSD is an elastic block storage device based on the distributed storage architecture. With standard SSDs, computing is separated from storage.

  • ESSD

    ESSD is a new SSD product launched by Alibaba Cloud. Enhanced SSD is designed based on the new generation of distributed block storage architecture. It integrates 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies to provide super high performance and lower latency. Each ESSD can process up to 1 million random read/write requests per second.

Note All of the three storage types meet the reliability, retainability, and read/write performance requirements specified in Alibaba Cloud SLA.
  • Local SSDs are used for RDS instances that work in primary/secondary mode. If the primary instance becomes faulty, the secondary instance takes over services within seconds. In the High-availability Edition, the database system consists of one primary instance and one secondary instance. In the Enterprise Edition, the database system consists of one primary instance and two secondary instances.
  • Standard SSDs and ESSDs both work in a distributed architecture to ensure data reliability by using multiple replicas. If the RDS instance with standard SSDs or ESSDs is in the Basic Edition, taking over services requires a long time in the event of a fault. If the RDS instance with standard SSDs or ESSDs is in the High-availability, Cluster, or Enterprise Edition, services can be taken over within seconds in the event of a fault.

View the storage type of an RDS instance

Log on to the ApsaraDB for RDS console, find the target RDS instance, and navigate to the Basic Information page. In the Basic Information section, view the storage type of the RDS instance.

Storage Type

Comparison

Table 1. Feature comparison
Item Local SSD Standard SSD ESSD
I/O performance

★★★★★

Provides low I/O latency and high I/O performance.

★★★★

Requires additional network I/O operations, which decreases I/O performance.

★★★★★

Provides higher I/O performance than standard SSDs.

Functionality

★★★★★

Supports all functions.

★★★

Does not support read/write splitting, SQL audit, or dedicated proxy for some database engines.

★★★

Does not support read/write splitting, SQL audit, or dedicated proxy for some database engines.

Configuration flexibility

★★★

Does not allow you to adjust the storage capacity of a dedicated instance. The storage capacity is determined by the instance type.

★★★★★

Provides a number of options to configure and allows you to adjust the storage capacity.

★★★★★

Provides a number of options to configure and allows you to adjust the storage capacity.

Scalability

★★★

Requires hours to copy data when you scale the database system.

★★★★★

Scales the database system within minutes.

★★★★★

Scales the database system within minutes.

Table 2. Function comparison
Item Local SSD Standard SSD and ESSD
Maximum storage capacity 6 TB 6 TB
Network type Classic Network and VPC Classic Network and VPC
Elastic upgrade and downgrade Supported (An elastic upgrade or downgrade can be completed within hours, based on the data volume.) Supported (An elastic upgrade or downgrade can be completed within 10 minutes.)
Zone migration Supported In development
Read-only instances Supported Supported for some database engines
Read/write splitting Supported Supported for some database engines
SQL audit Supported In development
SSL encryption and TDE Supported Supported for some database engines
Data backup Physical backup and logical backup Snapshot backup
Data restoration by backup set Supported Supported
Data restoration by time Supported Supported
Dedicated database proxy Supported for some database engines In development

Product support

The storage types supported vary according to the database engine version and RDS edition.

Database engine Version Edition Storage type
MySQL 8.0 Basic Edition Standard SSD
High-availability Edition ESSD
Standard SSD
Local SSD
5.7 Basic Edition Standard SSD
Enterprise Edition ESSD
Standard SSD
Local SSD
5.6 High-availability Edition Local SSD
5.5 High-availability Edition Local SSD
SQL Server 2017 Cluster Edition ESSD
Standard SSD
2016 Basic Edition and High-availability Edition ESSD
Standard SSD
2012 Basic Edition and High-availability Edition ESSD
Standard SSD
2008 R2 High-availability Edition Local SSD
PostgreSQL 10 and 9.4 High-availability Edition Local SSD
10 Basic Edition Standard SSD
PPAS 10 and 9.3 High-availability Edition Local SSD
MariaDB 10.3 High-availability Edition Standard SSD