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.
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):
For more information about ESSD performance, see ESSDs.
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 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.
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.
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.
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 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
Delivers higher I/O performance than standard SSDs.
Reduces I/O latencies and improves I/O performance.
Requires additional network I/O overheads, which decreases I/O performance.
Provides various configuration options and allows you to expand or reduce the storage capacity of an RDS instance.
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.
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
Transient connections occur during the storage capacity expansion process.
For more information about the storage types and the features that are supported by different database engines, see the following topics: