What Is EVS?

Overview

Elastic Volume Service (EVS) offers scalable block storage for cloud servers. With high reliability, high performance, and a variety of specifications, EVS disks can be used for distributed file systems, development and test environments, data warehouses, and high-performance computing (HPC) applications. Cloud 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 in this document.

Figure 1 EVS architecture

EVS Advantages

EVS has the following advantages:

**Table 1** EVS advantages
Advantage	Description	Related Knowledge
Various disk types	EVS provides a variety of disk types for you to choose from, and EVS disks can be used as data disks and system disks for servers. You can select an appropriate disk type that best suits your budget and service requirements.	Disk Types and Performance
Elastic scalability	The EVS disk capacity ranges from 10 GiB to 32 TiB. When it no longer meets your needs, you can expand the disk capacity up to 32 TiB in increments of 1 GiB, without interrupting your applications.	Expansion Overview
Elastic scalability	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 Encryption
High security and reliability	Data protection functions, such as backups and snapshots, safeguard the disk data, preventing incorrect data caused by application exceptions or attacks.	EVS 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

There are currently three types of storage available for you to choose from: EVS, Scalable File Service (SFS), and Object Storage Service (OBS). See their differences in the following table.

**Table 2** Comparison among SFS, OBS, and EVS
Dimension	SFS	OBS	EVS
Concept	SFS provides on-demand high-performance file storage, which can be shared by multiple servers. 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 a variety of 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 can be stored directly to OBS. The files automatically generate corresponding system metadata. You can also customize the metadata if needed.	Stores binary data and cannot directly store files. To store files, you need to format the file system first.
Access method	SFS file 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 Scenarios	Gene sequencing, image rendering, media processing, file sharing, content management, and web services	Big data analytics, 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
Capacity	Petabytes	Exabytes	Terabytes
Latency	3–10 ms	10 ms	1 ms
IOPS/TPS	10,000 for a single file system	Tens of millions	33,000 for a single disk
Bandwidth	GiB/s	TiB/s	MiB/s
Data sharing	Supported	Supported	Supported
Remote access	Supported	Supported	Not supported
Used independently	Supported	Supported	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 from the service list. If you do not have an account, register yourself on the public cloud.