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What Is Elastic Volume Service?

Updated at: Sep 02, 2021 GMT+08:00


Elastic Volume Service (EVS) offers scalable block storage for cloud servers. With high reliability, high performance, and rich specifications, EVS disks can be used for distributed file systems, development and testing environments, data warehouse applications, and high-performance computing (HPC) scenarios to meet diverse service requirements. Servers that EVS supports include Elastic Cloud Servers (ECSs) and Bare Metal Servers (BMSs).

EVS disks are similar to hard disks in PCs. They must be attached to servers for use and cannot be used alone. You can initialize EVS disks, create file systems on them, and store data persistently on them.

EVS disks are sometimes just referred to as disks.

Figure 1 EVS architecture

EVS Advantages

EVS has the following advantages:

Table 1 EVS advantages



Related Knowledge

Various disk types

EVS provides various disk types for you to choose from, and EVS disks can be used as data disks and system disks for servers. You may select the disk type based on your budget and service requirements.

Disk Types and Performance

Elastic scalability

The EVS disk capacity ranges from 10 GB to 32 TB. When it no longer meets your needs, you can expand the disk capacity up to 32 TB in increments of 1 GB, without interrupting your applications.

Expansion Overview

Besides the disk capacity limit, the additional space you can add cannot exceed the remaining quota. You can increase the quota if the remaining quota is insufficient.

Querying EVS Resource Quotas

High security and reliability

Both system disks and data disks support data encryption to ensure data security.

EVS Disk Encryption

Data protection functions, such as backups and snapshots, safeguard the disk data, preventing incorrect data caused by application exceptions or attacks.

EVS Disk Backup

EVS Snapshot (OBT)

Real-time monitoring

On Cloud Eye, you can monitor the disk health and operating status at any time.

Viewing EVS Monitoring Data

Differences Among EVS, SFS, and OBS

Currently, there are three data storage services available for you to choose from: EVS, Scalable File Service (SFS), and Object Storage Service (OBS). The differences are described in the following table.

Table 2 Comparison between SFS, OBS, and EVS






SFS provides on-demand high-performance file storage, which can be shared by multiple ECSs. SFS is similar to a remote directory for Windows or Linux OSs.

OBS provides massive, secure, reliable, and cost-effective data storage for users to store data of any type and size.

EVS provides scalable block storage that features high reliability and high performance to meet various service requirements. An EVS disk is similar to a hard disk on a PC.

Data storage logic

Stores files. Data is sorted and displayed in files and folders.

Stores objects. Files directly stored automatically generate the system metadata, which can also be customized by users.

Stores binary data and cannot directly store files. To store files, you need to format the file system first.

Access method

SFS systems can be accessed only after being mounted to ECSs or BMSs through NFS or CIFS. A network address must be specified or mapped to a local directory for access.

OBS buckets can be accessed through the Internet or Direct Connect. The bucket address must be specified for access, and transmission protocols HTTP and HTTPS are used.

EVS disks can be used and accessed from applications only after being attached to ECSs or BMSs and initialized.

Application Scenario

Gene sequencing, image rendering, media processing, file sharing, content management, and web services

Big data analysis, static website hosting, online video on demand (VoD), gene sequencing, and intelligent video surveillance

Industrial design, energy exploration, critical clustered applications, enterprise application systems, and development and testing






3–10 ms

10 ms

1 ms


10,000 for a single file system


33,000 for a single disk





Data sharing




Remote access



Not supported

Online editing


Not supported


Used independently



Not supported

Methods of Access

The public cloud system provides a web-based management console and HTTPS-based APIs for you to access the EVS service.

  • APIs

    Use APIs if you need to integrate EVS into a third-party system for secondary development. For details, see Elastic Volume Service API Reference.

  • Management console

    Use the management console if you do not need to integrate EVS with a third-party system. Log in to the management console with your account and choose Elastic Volume Service on the homepage. If you do not have an account, see Registering Yourself on the Public Cloud.

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