This topic describes what elastic volume service (EVS) is.

Elastic Volume Service (EVS) is an elastically scalable block storage device that provides high-performance and highly reliable block storage services for ECS instances and physical servers. eSurfing Cloud provides multiple EVS specifications to meet the business needs in different scenarios, including distributed file systems, databases, and development & test environments.

Users can operate and manage EVS disks online and can also format and create file systems on EVS mounted to cloud servers just like traditional server disks.

Architecture

EVS can be mounted to elastic cloud servers and physical servers. The backup and snapshot features of EVS help users restore data and create new EVS disks, providing powerful data protection and improving data reliability, flexibility, and disaster recovery capability.

Differences Among Elastic Volume Service, Scalable File Service, and Object Storage Service

eSurfing Cloud provides users with three data storage services, namely elastic volume service, scalable file service, object storage service. The main differences among these three services are as follows:

Scope	Scalable File Service	Object-Oriented Storage	EVS
Concept	SFS provides highly scalable file storage, allowing multiple ECS instances to access the same file system concurrently. It features high availability, data persistence, and reliability.	ZOS provides robust features, including high scalability and data persistence. It stores extensive amounts of data of any type. ZOS automatically processes data redundancy, fault recovery, and data distribution.	EVS provides high performance, low latency, and scalable block-level storage. EVS disks can be mounted to VM instances or physical servers to store data persistently.
Storage Mode	SFS uses file storage. File storage is organized in a hierarchical directory and file architecture. You can access directories and files using the file paths and names.	In ZOS, data is stored as independent objects. Each object consists of both data and the associated metadata. Metadata includes attributes such as the file name, file type, and file size.	EVS uses block storage. In block storage, data is divided into blocks of fixed size (several KBs or MBs) and accessed through a unique block address.
Access Mode	SFS enables data access through network sharing. Users can mount a scalable file service to an elastic cloud server instance or container instance and access the shared file system using standard file system interfaces, such as NFS and SMB.	You must specify a bucket address for the object storage service and the object storage service can be accessed using RESTful APIs over HTTP or HTTPS.	EVS disks are similar to disks in PCs, and they cannot be used independently. They are often mounted to ECS instances or physical servers to become visible in operating systems.
Scenario	Example scenarios include the storage of application configuration files and log files that need to be shared, as well as data sharing and synchronization between different container instances in containerized applications.	Example scenarios include large-scale data storage and analysis such as big data analysis, data lake, data backup and archive, as well as static website hosting storage.	Data storage and persistence in a data storage medium for a VM instance or a physical server, and high performance computing scenarios such as large-scale data processing and distributed computing.
Capacity	SFS provides dynamically scalable capacity, with the ability to scale up to 10 PB.	The object storage service has no capacity limit, and storage resources can be scaled up unlimitedly.	EVS allows on-demand capacity expansion, with a minimum expansion of 1 GB. Individual EVS disks can be expanded from an initial size of 10 GB up to an impressive 32 TB.
Whether data sharing is supported	Yes	Yes	Yes
Whether remote access is supported	Yes	Yes	No

Access Mode

In eSurfing Cloud, you can configure and manage EVS in the following ways:

Console: A Web-based service management platform, enabling you to configure and manage EVS disks in the management console.
API: In eSurfing Cloud, users can also access EVS by using APIs (application programming interface). For more information, see API Reference of EVS.

Elastic Volume Service

Overview