This topic describes the three types of storage media that are supported by ApsaraDB RDS. ApsaraDB RDS supports local SSDs, standard SSDs, and enhanced SSDs (ESSDs). These storage types meet the reliability, persistence, and read and write performance requirements that are specified in Alibaba Cloud service level agreement (SLA).

Introduction

ApsaraDB RDS provides these storage types to meet your business requirements in various scenarios.

  • Local SSDs

    Local SSDs are a recommended type of storage media. Local SSDs reside on the same physical host as the database engine that is used. You can store data on local SSDs to reduce I/O latencies.

  • Standard SSDs

    Standard SSDs are elastic block storage devices that are designed based on a distributed storage architecture. You can store data on standard SSDs to separate computing from storage.

  • ESSDs
    ESSDs are also a recommended type of storage media. ESSDs deliver ultra high storage performance. This storage type is developed by Alibaba Cloud based on the next-generation distributed block storage architecture. ESSDs are integrated with 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. ESSDs can help reduce one-way latencies and process up to 1 million read and write requests at random per second. ESSDs come in three performance levels (PLs) on the ApsaraDB RDS buy page:
    • ESSD PL1: This refers to ESSDs of PL1.
    • ESSD PL2: An ESSD of PL2 delivers IOPS and throughput that are about two times higher than the IOPS and throughput that are delivered by an ESSD of PL1.
    • ESSD PL3: An ESSD of PL3 delivers IOPS that is up to 20 times higher than the IOPS that is delivered by an ESSD of PL1. An ESSD of PL3 also delivers throughput that is up to 11 times higher than the throughput that is delivered by an ESSD of PL1. ESSDs of PL3 are suitable for business scenarios in which highly concurrent requests must be processed with high I/O performance and at low read and write latencies.

For more information about the differences in performance and use scenarios among these storage types, see EBS performance. The performance comparison items include the maximum capacity per disk, maximum IOPS, and maximum throughput.

Note All of these storage types meet the reliability, persistence, and read and write performance requirements that are specified in Alibaba Cloud SLA.
  • Local SSDs are suitable for the RDS High-availability Edition that provides one primary RDS instance and one secondary RDS instance and for the RDS Enterprise Edition that provides one primary RDS instance, one secondary RDS instance, and one logger RDS instance. Both RDS editions support failovers. If the primary RDS instance unexpectedly exits, your database system can fail over to the secondary instance within a few seconds.
  • Standard SSDs and ESSDs both work in a distributed storage architecture. This architecture ensures reliability by using multiple data copies. If you are using the RDS Basic Edition, the recovery from a fault requires a long period of time. If you are using the RDS High-availability Edition, RDS Cluster Edition, or RDS Enterprise Edition, your database system can fail over to the secondary RDS instance within a few seconds in the event of a fault.

View the storage type of an RDS instance

Log on to the ApsaraDB RDS console and go to the Basic Information page of the RDS instance. In the Basic Information section of the page, you can view the storage type of the RDS instance.

New ApsaraDB RDS console

Comparison between storage types

Table 1. Functionality comparison
Item Local SSD Standard SSD ESSD (recommended)
I/O performance

★★★★★

Helps reduce I/O latencies and improve I/O performance.

★★★★

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

★★★★★

Delivers higher I/O performance than standard SSDs.

Configuration flexibility

★★★★

Provides a number of configuration options and allows you to separately adjust the storage capacity. However, some instance types provide a fixed amount of storage capacity when these instance types are used with local SSDs.

★★★★★

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

★★★★★

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

Scalability

★★★

May require a few hours to copy data when you scale the database system.

★★★★★

Scales the database system within a few minutes.

★★★★★

Scales the database system within a few minutes.

Product support

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