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.
Functions
EVS provides various persistent storage devices. 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 are not 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 64 TB (in the KVM scenario) or 32 TB (in other scenarios). 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)..
