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FusionCloud 6.3.0 Solution Description 05

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What Is Elastic Volume Service?

What Is Elastic Volume Service?


Elastic Volume Service (EVS) is a virtual block storage service, which provides block storage space for Elastic Cloud Servers (ECSs) and Bare Metal Servers (BMSs). You can create EVS disks on the console and attach them to ECSs. The method for using EVS disks is the same as that for using hard disks on physical servers. EVS disks have higher data reliability and I/O throughput and are easier to use. EVS disks are suitable for file systems, databases, or system software or applications that require block storage devices.

In this document, an EVS disk is also referred to as a disk.

In this document, instances refer to the ECSs or BMSs that users apply for.


Various types of persistent EVS disks are available. You can choose disk types based on your needs and store files and build databases on EVS disks. EVS supports the following major features:

  • Elastic attaching and detaching

    An EVS disk is like an original unformatted block storage device, which can be attached to a single instance, for external data. Disks will not be affected by the running time of instances. After attaching a disk to an instance, you can use the disk as if you were using a physical hard disk. You can also detach a disk from an instance and attach the disk to another instance.

  • Various disk types

    A disk type represents backend storage devices used by a group of disks. You can divide disk types of EVS disks based on backend storage types to meet different performance requirements of services. When the read and write performance of the storage device no longer suits your services, you can change the disk type to alter the type of the storage media where the disk resides to change the read and write performance, meeting the requirements of the instance for higher storage service performance.

  • Scalability

    A single disk has a maximum capacity of 32 TB. You can configure storage capacity and expand the capacity on demand to deal with your service data increase.

  • Snapshot

    You can back up your data by taking a snapshot of disk data at a specific time. When data loss occurs due to tampering or misdeletion or a service fault occurs, you can use snapshots to roll back risks. You can also create new disks from snapshots and attach them to other instances to provide data resources for a variety of services, such as data mining, report query, and development and test. Snapshots can be used to protect original data or create new disks for rapidly deploying other services, meeting diversified service data requirements of enterprises.

  • Shared disk

    Multiple instances can access (read and write) a shared disk at the same time, meeting the requirements of key enterprises that use clusters and high availability (HA).

Differences between EVS, OBS, and SFS

Table 7-10 shows the differences between the EVS, OBS, and SFS.

Table 7-10 Differences between EVS, OBS, and SFS

Service Name


Application Scenario



A virtual block storage service that provides block storage space for ECSs or BMSs.

Applies to file systems, databases, or other system software or applications that require block storage devices.

  • In a similar way for traditional disks on servers, you can format EVS disks that are attached to Elastic Cloud Servers (ECSs), and create file systems on them.
  • A shared EVS disk can be attached to multiple ECSs to share data.
  • Data can only be accessed in the internal network of data centers.

Object Storage Service (OBS)

Object-based storage service. It provides you with massive, highly reliable, and secure data storage capabilities at low cost.

Applies to the storage of unstructured data such as documents, images, and audiovisual videos.

  • You have to use programming or third-party tools to access OBS.
  • Data sharing: All users can access shared object storage data by invoking the same path using servers, embedded devices, and IoT devices.
  • Data can be accessed on the Internet.

Scalable File Service (SFS)

High-performance file storage service that can be expanded on demand and can be shared by multiple ECSs on the cloud.

SFS applies to video cloud scenarios, and seamlessly handles data-intensive and bandwidth-intensive applications.

  • Complying with the standard file protocol, SFS mounts the file service to the server. In this way, you gain the same experience as using local file directories.
  • Data sharing: One file system can be attached to multiple servers. Data can be shared and accessed.
  • Data can only be accessed in the internal network of data centers.
Updated: 2019-04-23

Document ID: EDOC1100026685

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