Overview

Elastic Volume Service (EVS) provides scalable block storage for FlexusX instances. With high reliability, high performance, and varied specifications, EVS disks can be used for distributed file systems, development and testing environments, data warehouses, and high-performance computing (HPC) scenarios to meet diverse service requirements.

System and data disks of FlexusX instances support the following EVS disk types: common I/O, high I/O, General Purpose SSD, ultra-high I/O, and General Purpose SSD V2. By default, a FlexusX instance has a system disk attached. You can configure the type and capacity of the system and data disks based on service requirements. For more information about EVS disk performance, see Disk Types and Performance.

Billing

EVS disks are billed based on the disk type, size, and usage duration on a yearly/monthly or pay-per-use basis. For details about EVS billing, see Billing for EVS Disks.

Constraints

When you purchase a FlexusX instance, the EVS disk device type is VBD by default and cannot be changed. After purchasing a FlexusX instance, you can add SCSI data disks.
When you purchase a FlexusX instance, you can add a maximum of 24 disks (1 system disk and 23 data disks). After purchasing a FlexusX instance, you can add a maximum of 60 disks.
If more data disks are required, attach them after purchasing a FlexusX instance. To query the number of disks that can be attached to FlexusX instances of different specifications, see Querying Information About Disks Attached to an ECS.
After a new data disk is attached to a FlexusX instance, you need to initialize the data disk before using it.

For details about EVS constraints, see EVS Notes and Constraints.

Related Operations

Operation	Description
Adding an EVS Disk	You can purchase data disks when purchasing FlexusX instances, but the disks must be initialized before you can use them. You can also purchase data disks after purchasing FlexusX instances. Disks created from data sources, such as backups or snapshots, do not need to be initialized. Disks that are not created from data sources must be initialized before you can use them.
Attaching an EVS Disk	After a FlexusX instance is created, if the EVS disks on the instance cannot meet service requirements, you can attach existing disks to the FlexusX instance.
Detaching an EVS Disk	If a file system on your system disk is damaged and your FlexusX instance cannot be started, you can detach the system disk and attach it to another FlexusX instance as a data disk. After the file system is fixed, you can attach the disk back to the original FlexusX instance as the system disk. If you want to move a data disk from one FlexusX instance to another in the same region and AZ, you can detach the data disk and then attach it to that FlexusX instance. If you no longer need an EVS disk, you can detach and delete it.
Expanding the EVS Disk Capacity	If the disk capacity of your FlexusX instance is not enough, you can expand the capacity.
Initializing a Data Disk	Data disks must be initialized before they can be used, regardless of whether they are created together with FlexusX instances or created separately and attached to the FlexusX instances. An initialized data disk does not need to be initialized again. NOTE: System disks do not need to be initialized. Data disks containing data do not need to be initialized.