ApsaraDB for RDS supports three types of storage media. They are 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

These storage types are provided to meet your specific business requirements in various scenarios.

  • Local SSD

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

  • Standard SSD

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

  • Enhanced SSD
    This is also a recommended storage type. This new SSD product is designed by Alibaba Cloud based on the 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. Supported enhanced SSDs come in the following three performance levels (PLs):
    • PL1: An enhanced SSD of PL1 is a regular enhanced SSD.
    • 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 workloads that require high I/O performance in processing concurrent requests and stable read/write latency.
    For more information about PLs, see 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 RDS High-availability Edition that allows for one primary instance and one secondary instance. This type of SSD is also suitable for the RDS 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 allows you to ensure reliability by using multiple data copies. If you are using the RDS Basic Edition, your database system requires a long period of time to recover from a fault. If you are using the RDS High-availability, Cluster, or Enterprise Edition, your database system can fail 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, go to the Basic Information page of the RDS instance, and in the Basic Information section view the storage type of the RDS instance.

View the storage type of an RDS instance

Comparison between storage types

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

★★★★★

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

★★★★

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

★★★★★

Provides higher I/O performance than a standard SSD.

Configuration flexibility

★★★★

Provides a number of configuration options and allows you to adjust the storage capacity. However, some instance types provide a specific amount of storage capacity that cannot be adjusted.

★★★★★

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: