Introduction and purchase suggestions for ApsaraDB RDS for SQL Server storage types-ApsaraDB RDS(RDS)-阿里云帮助中心

ApsaraDB RDS for SQL Server provides two data storage types: Enhanced SSDs (ESSDs) and premium performance disks. This topic describes the basic features and differences of these storage types and provides purchase suggestions.

Introduction to storage types

Note

For more information about the performance comparison of different storage types, such as maximum capacity per disk, maximum IOPS, and maximum throughput, see Block storage performance.
The reliability, durability, and read/write performance of disks (ESSDs and premium performance disks) meet the requirements specified in the product Service-Level Agreement (SLA). These disks use a distributed architecture and multiple replicas to ensure data reliability. If your RDS instance runs RDS High-availability Edition or RDS Cluster Edition, an automatic switchover can be completed in seconds.

ESSDs

Enhanced SSD (ESSD) is a new ultra-high performance cloud disk product from Alibaba Cloud. Based on a new-generation distributed block storage architecture, ESSDs use 25GE networks and Remote Direct Memory Access (RDMA) technology. They provide up to 1 million random read/write input/output operations per second (IOPS) for a single disk and lower one-way latency than standard SSDs. ESSDs are available in the following categories:

PL1 ESSD: An ESSD at performance level (PL) 1.
PL2 ESSD: Compared to PL1, a PL2 ESSD increases IOPS and throughput by about two times.
PL3 ESSD: Compared to PL1, a PL3 ESSD increases IOPS by up to 20 times and throughput by up to 11 times. It is suitable for business scenarios that require extremely high concurrent I/O performance and stable read/write latency.

For more information about the performance of ESSDs, see ESSDs.

Premium performance disks

Premium performance disks provide the same basic capabilities as PL1 ESSDs. Premium performance disks are compatible with all features of ESSDs, except for the feature that lets you pause an instance. Premium performance disks provide the performance burst feature and the data archiving to OSS feature to meet more business requirements.

View the storage type

You can view the storage type of an instance on the Basic Information page.

Performance data of storage types

Comparison item	ESSD	Premium performance disk
I/O performance	★★★★★ Significant improvement over standard SSDs: IOPS: Varies based on the disk specifications and instance type. I/O latency: 100 to 200 microseconds	★★★★★★ This storage type is based on ESSDs and provides the performance burst and data archiving to OSS features. Its I/O performance is as follows: IOPS: Varies based on the disk specifications and instance type. I/O latency: 100 to 200 microseconds
Configuration flexibility	★★★★★ Provides various configuration options and supports storage capacity scale-out.	★★★★★ Provides various configuration options and supports storage capacity scale-out.
Backup method	Snapshot backup for ESSDs	Snapshot backup for ESSDs
Speed of backup, read-only instance creation, and instance cloning	★★★★★ The operations can be completed in seconds.	★★★★★ The operations can be completed in seconds.
Scale-out duration	★★★★★ Online upgrade. The scale-out can be completed in seconds.	★★★★★ Online upgrade. The scale-out can be completed in seconds.
Impact of scale-out	No impact.	No impact.
Data durability	★★★★★ Provides 99.9999999% data reliability. Supports single-node instances of Basic Edition to reduce costs.	★★★★★ Provides 99.9999999% data reliability. Supports single-node instances of Basic Edition to reduce costs.

Purchase suggestions

We recommend selecting premium performance disks. If your I/O performance fluctuates significantly and you want to reduce storage costs, enable the performance burst and data archiving to OSS features.
If you require disks with a high PL, select ESSDs.

References

For more information, see FAQs about buckets.