DB Instance Storage Types

The database system is generally an important part of an IT system and has high requirements on storage I/O performance. You can select a storage type based on service demands. You cannot change the storage type after the DB instance is created.

Description

RDS supports Cloud SSD (also called Ultra-high I/O) and Extreme SSD to suit different performance requirements of your workloads.

Cloud SSD or Ultra-high I/O
Stores data in cloud disks for decoupled storage and compute. The maximum throughput is 350 MB/s.
- For RDS for MySQL instances, this storage type is normally displayed as Cloud SSD, but for existing instances in certain regions it is displayed as Ultra-high I/O.
- For RDS for MariaDB, RDS for PostgreSQL and RDS for SQL Server instances, this storage type is displayed as Cloud SSD.
- The supported IOPS depends on the I/O performance of the Elastic Volume Service (EVS) disk. For details, see "Ultra-high I/O" in Disk Types and Performance of the Elastic Volume Service Service Overview.
Extreme SSD
Uses 25GE network and RDMA technologies to provide you with up to 1,000 MB/s throughput per disk and sub-millisecond latency.
- Only RDS for MySQL, RDS for SQL Server, and RDS for PostgreSQL support extreme SSDs.
- The supported IOPS depends on the I/O performance of the EVS disk. For details, see "Extreme SSD" in Disk Types and Performance of the Elastic Volume Service Service Overview.
Extreme SSD V2
Extreme SSD V2: supports super-high IOPS and throughput as well as super-low latency for the most performance-demanding workloads.

With the Extreme SSD V2 type, you can buy disks with the IOPS tailored to your workloads. The disk performance no longer changes with the disk capacity.

Extreme SSD V2 is now available only in CN South-Guangzhou. To use this storage type, contact customer service.

Extreme SSD V2 disks with a preconfigured IOPS higher than 128,000 can only reach the maximum performance on AC7 compute resources. To use such disks, contact customer service.
- Only RDS for SQL Server supports extreme SSD V2 disks.
- The supported IOPS depends on the I/O performance of the EVS disk. For details, see "Extreme SSD" in Disk Types and Performance of the Elastic Volume Service Service Overview.

Performance Comparison

**Table 1** Performance comparison
Item	Cloud SSD	Extreme SSD	Extreme SSD V2
I/O performance	Sub-par I/O performance due to additional network I/O overheads	Higher I/O performance than cloud SSDs	Higher I/O performance than cloud SSDs
Elastic scalability	Scaling in seconds	Scaling in seconds	Scaling in minutes
Maximum IOPS	50,000	128,000	Smaller value: min(256000, Storage space x 1000) You can buy disks with the IOPS tailored to your workloads. IOPS is separately billed on a pay-per-use basis.
Maximum throughput	350 MB/s	1,000 MB/s	4,000 MB/s
Read/write latency	1 ms	Sub-millisecond	Sub-millisecond