Help Center/ Elastic Cloud Server/ API Reference/ APIs/ Disk Management/ Attaching a Disk to an ECS
Updated on 2025-08-20 GMT+08:00
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Attaching a Disk to an ECS

Function

This API is used to attach a disk to an ECS.

This API is an asynchronous API. After the attachment request is successfully delivered, a job ID is returned. This does not mean the attachment is complete. You need to call the API by referring to Querying Job Execution Status to query the job status. The SUCCESS status indicates that the attachment is successful.

URI

POST /v1/{project_id}/cloudservers/{server_id}/attachvolume

Table 1 describes the parameters in the URI.
Table 1 Parameter description

Parameter

Mandatory

Description

project_id

Yes

Specifies the project ID.

For details about how to obtain the ID, see Obtaining a Project ID.

server_id

Yes

Specifies the ECS ID.

Request

Table 2 Request parameters

Parameter

Mandatory

Type

Description

volumeAttachment

Yes

Object

Specifies the ECS attachment information. For details, see Table 3.

dry_run

No

Boolean

Specifies whether to check the request and attach the disk.

  • true: indicates that only the request is sent, and no disk will be attached. Check items include mandatory parameters, request format, and service restrictions. If the check fails, the system returns an error. If the check result is as expected, the system properly responds.
  • false: indicates that only the request is sent and the disk will be attached if the check result is as expected.

The default value is false.
Table 3 volumeAttachment field description

Parameter

Mandatory

Type

Description

volumeId

Yes

String

Specifies the ID of the disk to be attached. The value is in UUID format.

device

No

String

Indicates the disk device name.

NOTE:
  • The new disk device name cannot be the same as an existing one.
  • This parameter is mandatory for Xen ECSs. Set the parameter value to /dev/sda for the system disks of such ECSs and to /dev/sdx for data disks, where x is a letter in alphabetical order. For example, if there are two data disks, set the device names of the two data disks to /dev/sdb and /dev/sdc, respectively. If you set a device name starting with /dev/vd, the system uses /dev/sd by default.
  • For KVM ECSs, set the parameter value to /dev/vda for system disks. The device names for data disks of KVM ECSs are optional. If the device names of data disks are required, set them in alphabetical order. For example, if there are two data disks, set the device names of the two data disks to /dev/vdb and /dev/vdc, respectively. If you set a device name starting with /dev/sd, the system uses /dev/vd by default.
  • For ECSs that only support SCSI disks, set the device name of the system disk to /dev/sda and the device names of data disks in alphabetical order, for example, /dev/sdb and /dev/sdc. The system will not change the default device names.

volume_type

No

String

Specifies the disk type.

count

No

Integer

Specifies the number of disks.

hw:passthrough

No

String
  • If this parameter is set to true, the disk device type is SCSI, which allows ECS OSs to directly access the underlying storage media. SCSI reservation commands are supported.
  • If this parameter is set to false, the disk device type is VBD, which supports only simple SCSI read/write commands.

Response

See Responses (Task).

Example Request

  • Attach a SCSI EVS disk to device /dev/sda. 
    POST https://{endpoint}/v1/{project_id}/cloudservers/{server_id}/attachvolume

{
    "volumeAttachment": {
         "volumeId": "a26887c6-c47b-4654-abb5-dfadf7d3f803",
         "device": "/dev/sda",
         "volume_type": "SSD",
         "count": 5,
         "hw:passthrough": "true"
    },
    "dry_run": false
}
  • Send a pre-check request for attaching a disk. 
    POST https://{endpoint}/v1/{project_id}/cloudservers/{server_id}/attachvolume

{
    "volumeAttachment": {
         "volumeId": "a26887c6-c47b-4654-abb5-dfadf7d3f803",
         "volume_type": "SSD",
         "count": 1,
         "hw:passthrough": "true"
    },
    "dry_run": true
}

Example Response

{
    "job_id": "ff80808288d41e1b018990260955686a"
}

Returned Values

See Returned Values for General Requests.

Error Codes

See Error Codes.

Parent topic: Disk Management