• Elastic Volume Service

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  2. Elastic Volume Service
  3. User Guide
  4. Overview
  5. What Is Elastic Volume Service?

What Is Elastic Volume Service?

Elastic Volume Service (EVS) offers scalable block storage for 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 sometimes just referred to as disks in this document.

Figure 1 EVS architecture

Function Characteristics

EVS provides disk resources for servers, and its function characteristics are as follows:

  • Various disk types

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

  • Elastic scalability

    The capacity of an EVS disk you can create ranges from 10 GB to 32 TB. You can expand the disk capacity if it fails to meet your service requirements. The minimum expansion increment is 1 GB, and an EVS disk can be expanded to a maximum of 32 TB. EVS also supports smooth expansion for disks without interrupting services.

    When you expand the capacity of a disk, the additional capacity is also affected by the capacity quota. The system will prompt you with the remaining capacity, and the additional capacity cannot exceed the remaining capacity. You can increase the quota to meet service requirements.

  • Security and reliability
    • Both system disks and data disks support data encryption, ensuring data security.
    • Data protection functions, such as backups and snapshots, can safeguard the EVS disk data, preventing incorrect data caused by application exceptions or attacks.
  • Real-time monitoring

    Working with Cloud Eye, EVS allows you to monitor the disk health and operating status at any time.

Differences Among EVS, SFS, and OBS

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

Table 1 Differences among EVS, SFS, and OBS


Overall Introduction

Typical Application Scenarios

Storage Capacity


EVS provides scalable block storage that features high reliability, high performance, and rich specifications for servers.

  • Enterprise office applications
  • Development and testing
  • Enterprise applications, include SAP, Microsoft Exchange, and Microsoft SharePoint
  • Distributed file systems
  • Various databases, include MongoDB, Oracle, SQL Server, MySQL, and PostgreSQL

EVS disks start at 10 GB and can be expanded as required in 1 GB increments to a maximum of 32 TB.


SFS provides completely hosted sharable file storage for ECSs. Compatible with the Network File System (NFS) protocol, SFS is expandable to petabytes and seamlessly handles data-intensive and bandwidth-intensive applications.

  • HPC scenarios, such as gene sequencing, animation rendering, and CAD/CAE
  • File sharing
  • Media processing
  • Content management and web services
  • Offline file backup

SFS storage capacity is available on demand and can be expanded to 10 PB at most.


OBS provides cloud storage for unstructured data, such as files, pictures, and videos. With multiple options for migration to the cloud, OBS provides low-cost, reliable storage access for massive data and supports online multimedia processing.

  • Enterprise backup and archive
  • Big data analysis
  • Enterprise cloud box
  • Static website hosting
  • Native cloud applications

OBS provides limitless storage capacity, and storage resources are available for linear and nearly infinite expansion.

User Permissions

Users with resource management permissions can control the operations performed on cloud service resources. For EVS, a user with the Server Administrator permission can perform operations on EVS disks, including creating EVS disks, deleting EVS disks, and creating EVS snapshots.

For details about user permissions, see Permissions.


A project is used to group and isolate OpenStack resources, including computing, storage, and network resources. A project can be a department or a project team. You can access IAM with a security administrator to create projects in a region and perform isolated management of resources. For details about projects, see Managing Projects.