Storage types - ApsaraDB RDS - Alibaba Cloud Documentation Center

ApsaraDB RDS provides three options for storage: local SSD, standard SSD, and enhanced SSD (ESSD). This topic describes the differences between the three storage types and purchase suggestions.

Introduction

Storage type	Description
ESSD	ESSDs are developed by Alibaba Cloud based on the next-generation distributed block storage architecture. ESSDs deliver ultra high storage performance. ESSDs are integrated with 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. ESSDs can help you reduce one-way latencies and process up to 1 million read and write requests at random per second. ESSDs are provided in the following performance levels (PLs): PL1 ESSD: This is the basic PL of ESSDs. PL2 ESSD: A PL2 ESSD delivers IOPS and throughput that are approximately twice the IOPS and throughput delivered by a PL1 ESSD. PL3 ESSD: A PL3 ESSD delivers IOPS that is up to 20 times the IOPS delivered by a PL1 ESSD. A PL3 ESSD also delivers throughput that is up to 11 times the throughput delivered by a PL1 ESSD. PL3 ESSDs 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 ESSD performance, see ESSDs.
Local SSD	Local SSDs reside on the same physical host as the database engine of your RDS instance. You can store data in local SSDs to reduce I/O latencies.
Standard SSD	Standard SSDs are elastic block storage devices that are designed based on a distributed storage architecture. You can store data in standard SSDs to separate computing from storage. Note Standard SSDs are being phased out. We recommend that you use ESSDs. For more information, see [Notice] End of sale for the standard SSD storage type for specific database engines in ApsaraDB RDS.

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

Note

All of the preceding storage types meet the reliability, durability, and read and write performance requirements that are specified in the ApsaraDB RDS SLA.

Local SSDs are used by RDS instances that run RDS High-availability Edition. In RDS High-availability Edition, a primary RDS instance and a secondary RDS instance are provisioned to implement high availability. If the primary RDS instance fails, a primary/secondary switchover is performed within seconds. For more information, see RDS High-availability Edition.
Standard SSDs and ESSDs both use a distributed storage architecture. This architecture supports multiple data copies, which are used to ensure data reliability. If the RDS instance runs RDS High-availability Edition or RDS Cluster Edition, a primary/secondary switchover is performed within seconds if the primary RDS instance fails.

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, view the storage type of the RDS instance.

Comparison between storage types

Item	ESSD	Local SSD	Standard SSD
I/O performance	★★★★★ Delivers higher I/O performance than standard SSDs.	★★★★★ Helps reduce I/O latencies and improve I/O performance.	★★★★ Requires additional network I/O overheads, which decreases I/O performance.
Configuration flexibility	★★★★★ Provides various configuration options and allows you to expand or reduce the storage capacity of an RDS instance. Note You can reduce the storage capacity of an RDS instance that runs MySQL or PostgreSQL and meets specific requirements. For more information, see Configuration items for an ApsaraDB RDS for MySQL instance and Change the specifications of an ApsaraDB RDS for PostgreSQL instance.	★★★★ Provides various configuration options and allows you to separately adjust the storage capacity. The storage capacity of some RDS instances that use local SSDs varies based on the instance types of the RDS instances. You cannot separately adjust the storage capacity of these RDS instances.	★★★★★ Provides various configuration options and allows you to separately expand the storage capacity. The storage capacity cannot be reduced.
Scalability	★★★★★ If your RDS instance runs MySQL, PostgreSQL, or MariaDB, online storage capacity expansion is supported, and you can expand the storage capacity of your RDS instance within a few seconds. If your RDS instance runs SQL Server, you can expand the storage capacity of your RDS instance within a few minutes.	★★★ Requires a few hours to expand the storage capacity of your RDS instance because the data needs to be replicated.	★★★★★ If your RDS instance runs MySQL, PostgreSQL, or MariaDB, online storage capacity expansion is supported, and you can expand the storage capacity of your RDS instance within a few seconds. If your RDS instance runs SQL Server, you can expand the storage capacity of your RDS instance within a few minutes.
Impact of storage capacity expansion	If your RDS instance runs MySQL, PostgreSQL, or MariaDB, your workloads are not affected. If your RDS instance runs SQL Server, transient connections occur during the storage capacity expansion process.	Transient connections occur during the storage capacity expansion process.	If your RDS instance runs MySQL, PostgreSQL, or MariaDB, your workloads are not affected. If your RDS instance runs SQL Server, transient connections occur during the storage capacity expansion process.

Product support

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

FAQ

FAQ about storage capacity