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What Is Elastic Volume Service?

Updated at: Jan 08, 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 provides disk resources for servers, and its advantages are as follows:

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 Disk Performance

Elastic scalability

The capacity of an EVS disk you can create ranges from 10 GB to 32 TB. Expand the disk capacity when it no longer meets your needs. The minimum expansion increment is 1 GB, and a disk can be expanded to up to 32 TB. EVS also supports smooth capacity expansion without interrupting services.

Expansion Overview

Besides the disk capacity limit, the additional space you can add during an expansion is also affected by the capacity quota. The system will prompt you with the remaining quota, and the space added cannot exceed that. You may increase the quota if you want to expand your disk but 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

Working with Cloud Eye, EVS allows you to 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 capabilities for users to store data of any type and size.

EVS provides scalable block storage that features high reliability, high performance, and rich specifications for ECSs to meet service requirements in different scenarios. An EVS disk is similar to a hard disk on a PC.

Data storage logic

Stores files and sorts and displays data in the hierarchy of files and folders.

Stores objects. Files can be directly stored. The files automatically generate corresponding system metadata. Users can also customize the metadata of files.

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

Access method

Attach file systems to ECSs. You need to specify a network address for access or change the network address to a local directory for access. The NFS and CIFS protocols are used.

You can access OBS through the Internet or Direct Connect. You need to specify the bucket address for access. The transmission protocols such as HTTP and HTTPS are used.

An EVS disk can only be used by mounting to an ECS or BMS and cannot be directly accessed by OS applications. It must be formatted into a file system for access.

Application Scenario

High-performance computing (HPC), media processing, file sharing, content management, and web services


HPC: High bandwidth is required for shared file storage, such as gene sequencing and image rendering.

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

HPC, enterprise core cluster applications, enterprise application systems, and development and testing


HPC: High-speed and high-IOPS storage is required, such as industrial design and energy exploration.






3–10 ms

10 ms

1–2 ms


10,000 for a single file system


33,000 for a single disk





Data sharing supported




Remote access supported




Online editing supported




Used independently




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. If you have registered with the public cloud, log in to the management console and choose Elastic Volume Service on the homepage. If not, see Registering Yourself on the Public Cloud.

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