Differences among the storage types of ApsaraDB RDS and purchase suggestions - ApsaraDB RDS

ApsaraDB RDS provides the Enterprise SSD (ESSD), local SSD, and standard SSD storage types. This topic provides basic information about the storage types, describes the differences among the storage types, and offers purchase suggestions.

Introduction

Storage type	Description	Supported database engine
Enterprise SSD (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 provide lower one-way latencies than standard SSDs and process up to 1 million read and write requests at random per second. ESSDs are provided at the following performance levels (PLs): PL1 ESSD: This is the basic PL of ESSDs. PL2 ESSD: A PL2 ESSD delivers input/output operations per second (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 and delivers throughput that is up to 11 times the throughput delivered by a PL1 ESSD. PL3 ESSDs are suitable for 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.	MySQL, PostgreSQL, SQL Server, and MariaDB
Local SSD	Local SSDs reside on the same physical host as the database engine that is run by your RDS instance. You can store data in local SSDs to reduce I/O latencies.	MySQL
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 [EOS/Discontinuation] End of sale for the standard SSD storage type for specific database engines in ApsaraDB RDS from July 01, 2022.	MySQL, PostgreSQL, SQL Server, and MariaDB
General ESSD	General ESSDs are compatible with all features of ESSDs and support the I/O burst, I/O acceleration, and data archiving features. I/O burst: This feature is supported for RDS instances that run MySQL and PostgreSQL. After you enable the feature for your RDS instance, the IOPS of general ESSDs is no longer limited by the maximum IOPS. This improves the I/O performance of the RDS instance to handle workload bursts during peak hours. I/O acceleration: This feature is supported for RDS instances that run MySQL and PostgreSQL. After you enable the feature for your RDS instance, the disk I/O efficiency and the response speed of the system are improved. This feature helps increase the size of the buffer pool, implement cache acceleration, and improve the read and write performance of the RDS instance. Data archiving: This feature is supported for RDS instances that run MySQL and PostgreSQL. After you enable the feature for your RDS instance, data that is infrequently accessed is archived to Object Storage Service (OSS) buckets, and the storage cost of the RDS instance is 80% lower the storage cost when you use PL1 ESSDs. The feature is suitable if your RDS instance contains infrequently accessed or modified tables. For more information, see General ESSDs of ApsaraDB RDS for MySQL and General ESSDs of ApsaraDB RDS for PostgreSQL. Note In ApsaraDB RDS for MySQL and ApsaraDB RDS for PostgreSQL, the general ESSDs provide higher baseline I/O performance than PL1 ESSDs. For more information, see [Product changes/Feature changes] The baseline I/O performance of the general ESSDs of ApsaraDB RDS instances is increased.	MySQL and PostgreSQL

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, persistence and read/write performance goals that are specified in Alibaba Cloud service level agreement (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 you use RDS High-availability Edition or RDS Cluster Edition and the primary RDS instance fails, a primary/secondary switchover is performed within seconds.

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

Note

Only RDS instances that run MySQL on RDS High-availability Edition support local SSDs.

Item	ESSD	Local SSD
I/O performance Note The I/O performance of a disk includes the metrics related to the speed and efficiency of the disk in reading or writing data, such as the IOPS, throughput, and latency.	★★★★★ Delivers higher I/O performance than standard SSDs. IOPS: varies based on the disk specifications and instance types. I/O latency: ranges from 100 to 200 microseconds.	★★★★★ Delivers low I/O latency and high I/O performance. IOPS: varies based on the instance types. I/O latency: ranges from 10 to 50 microseconds
Configuration flexibility	★★★★★ Provides various configuration options and allow 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 the RDS instances.
Backup method	Provides snapshot backups.	Provides physical backups by using XtraBackup.
Time required for backup, read-only instance creation, and instance cloning	★★★★★ Requires a few seconds.	★★ Requires a few hours based on the disk space.
Time required for storage capacity expansion	★★★★★ 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.
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.	Triggers transient connections during storage capacity expansion.
Data durability	★★★★★ Delivers 99.9999999% data reliability, supports RDS instances that run RDS Basic Edition, and reduces costs.	★★★★ Has a risk of data corruption due to hardware faults, which requires secondary databases to support disaster recovery.

Purchase suggestions

We recommend that you use ESSDs.

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