ApsaraDB RDS provides two types of storage: local SSDs and cloud SSDs.

  • Local SSD (recommended)

    A local SSD is in the server node where database engine resides. With local SSDs, computing is close to data so that I/O latency is reduced.

  • Cloud SSD

    A cloud SSD is an elastic block storage device based on the distributed storage architecture. With cloud SSDs, computing is separated from storage.

Note The reliability and availability of local SSDs and cloud SSDs are as follows:
  • Local SSDs: used for RDS instances that work in master/slave mode. If the master node becomes faulty, the slave node takes over services in seconds. For more information, see Product series overview.
  • Cloud SSDs: work in a distributed architecture to ensure data reliability through multiple replicas. If the RDS instance to which cloud SSDs belong is in Basic Edition, recovering services takes a long time in the event of a fault. If the RDS instance to which cloud SSDs belong is in High-availability Edition or Cluster Edition, services can be taken over in seconds in the event of a fault.

No matter which type of storage you choose, Alibaba Cloud ensures that RDS provides reliability, availability, and read/write performance that meet SLA requirements.

Comparison

Table 1. Feature comparison
Item Local SSD Cloud SSD
I/O performance ★★★★★

Low I/O latency and good performance.

★★★★

Performance is slightly lower due to additional network I/O.

Functionality ★★★★★

Supports all features of RDS.

★★★

Currently certain database engines do not support read/write splitting and SQL audit.

Configuration flexibility ★★★

The storage capacity of an dedicated instance depends on the instance specification and therefore cannot be adjusted without changing the instance specification.

★★★★★

There are more optional configurations, and the storage capacity can be adjusted separately.

Scalability ★★★

Scaling requires data replication and may take a few hours.

★★★★★

Scaling can be completed in minutes.

Table 2. Function comparison
Item Local SSD Cloud SSD
Maximum storage capacity 6 TB 6 TB
Network type Classic network and VPC Classic network and VPC
Elastic upgrade and downgrade Supported (An elastic upgrade or downgrade can be completed in hours, depending on the data volume.) Supported (An elastic upgrade or downgrade can be completed in 10 minutes.)
Zone migration Supported In development
Introduction to MySQL read-only instances Supported Supported by some database engines
Introduction to read/write splitting Supported Supported by some database engines
SQL audit Supported In development
Set SSL encryption and TDE Supported Supported by some database engines
Back up RDS data Physical backup and logical backup Snapshot backup
Restore MySQL data Supported Supported
Restore MySQL data Supported Supported

Product support

The supported storage types depend on the database engine, version, and series.

Database engine Version Series Storage type
MySQL 8.0 High-availability Edition Cloud SSD
Local SSD
5.7 Basic Edition Cloud SSD
High-availability Edition Cloud SSD
Local SSD
5.6 High-availability Edition Local SSD
5.5 High-availability Edition Local SSD
SQL Server 2017 Cluster Edition Cloud SSD
2016 Basic Edition/High-availability Edition Cloud SSD
2012 Basic Edition/High-availability Edition Cloud SSD
2008 R2 High-availability Edition Local SSD
PostgreSQL 10、9.4 High-availability Edition Local SSD
10 Basic Edition Cloud SSD
PPAS 10 High-availability Edition Local SSD
MariaDB 10.3 High-availability Edition Cloud SSD