This topic describes the storage types supported by ApsaraDB for RDS, including local SSDs, standard SSDs, and enhanced SSDs. All of these storage types meet the reliability, persistence, and read/write performance requirements that are specified in Alibaba Cloud service-level agreement (SLA).

Introduction

The scenarios for which these storage types are suitable are as follows:

  • Local SSDs

    This is a recommended storage type. A local SSD resides on the same server as the database engine. You can store data on a local SSD to reduce I/O latency.

  • Standard SSDs

    A standard SSD is an elastic block storage device that is designed based on a distributed storage architecture. You can store data on a standard SSD to separate computing from storage.

  • Enhanced SSDs (Recommended)
    This is also a recommended storage type. This new SSD product is designed by Alibaba Cloud based on next-generation distributed block storage architecture. It integrates 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies to provide super high performance at low latency. An enhanced SSD can process up to 1 million random read/write requests per second. Enhanced SSDs come in three performance levels (PLs):
    • PL1: Enhanced SSDs of PL1 are regular enhanced SSDs.
    • PL2: An enhanced SSD of PL2 delivers input/output operations per second (IOPS) and throughput that are twice as high as those delivered by an enhanced SSD of PL1.
    • PL3: An enhanced SSD of PL3 delivers IOPS that is 20 times as high as the IOPS delivered by an enhanced SSD of PL1. It also delivers throughput that is 11 times as high as the throughput delivered by an enhanced SSD of PL1. Enhanced SSDs of PL3 are ideal for businesses that require high I/O performance in processing concurrent requests without increasing read/write latency.
    For more information about PLs, see block Block storage performance.
Note All of these storage types meet the reliability, persistence, and read/write performance requirements that are specified in Alibaba Cloud SLA.
  • Local SSDs: This type of SSD is suitable for the High-availability Edition that allows for one primary instance and one secondary instance and the Enterprise Edition that allows for one primary instance and two secondary instances. Both editions support failovers. If the primary instance becomes faulty, your database system fails over to a secondary instance in seconds.
  • Standard and enhanced SSDs: Both types of SSDs work in a distributed storage architecture. This architecture uses multiple data copies to ensure reliability. If your database system is running the Basic Edition, a service recovery from a fault requires a long period of time. If your database system is running the High-availability, Cluster, or Enterprise Edition, your database system fails over to a secondary instance in 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, you can view the storage type of the RDS instance.

View the storage type of an RDS instance

Comparison

Table 1. Feature comparison
Item Local SSD Standard SSD Enhanced SSD (Recommended)
I/O performance

★★★★★

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

★★★★

Incurs additional network I/O overheads, which decrease I/O performance.

★★★★★

Provides higher I/O performance than a standard SSD.

Configuration flexibility

★★★

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

★★★★★

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

★★★★★

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

Scalability

★★★

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

★★★★★

Allows you to scale the database system in minutes.

★★★★★

Allows you to scale the database system in minutes.

Product support

For more information about the storage types and features that are supported by various database engines, see the following topics: