Hello, Pupu!
I have one picture that describes the meaning and supported operations of each state.

EVS disk status description
EVS Disk Status | Status Description | Supported Operation |
---|
In-use | The EVS disk is attached to an instance and is in use. | |
Downloading | Data is being downloaded from an image to the EVS disk. An EVS disk is in this status when you are creating an ECS. | - |
Available | The EVS disk is created and has not been attached to any server. | |
Creating | The EVS disk is being created. | - |
Attaching | The EVS disk is being attached to an instance. | - |
Detaching | The EVS disk is being detached from an instance. | - |
Deleting | The EVS disk is being deleted. | - |
Extending | The capacity of the EVS disk is being expanded. | - |
Rolling back | The EVS disk data is being rolled back using the snapshot. | - |
Backing up | The EVS disk is being backed up. | - |
Restoring | The EVS disk data is being restored using the backup. | - |
Retyping | The EVS disk type is being changed. | - |
Soft deleted | The EVS disk has been soft deleted and moved to the recycle bin. | Restore Permanently delete
|
Error | An error occurs when you are creating an EVS disk. You can delete the EVS disk and create it again. | Delete |
Deletion failed | An error occurs when you are deleting an EVS disk. Contact the administrator. | None |
Expansion failed | An error occurs when you are expanding the capacity of an EVS disk. The administrator will contact you and help you handle this error. Do not perform any operations on the disk before the administrator contact you. If you require that the error be handled as soon as possible, contact the administrator. | - |
Rollback failed | An error occurs during an EVS disk rollback. | Delete |
Restoration failed | An error occurs during EVS disk restoration. The administrator will contact you and help you handle this error. Do not perform any operations on the disk before the administrator contact you. If you require that the error be handled as soon as possible, contact the administrator. | Delete |
Maintenance | The EVS disk is being migrated. | - |
Reserved | Status of the source disk after the migration task is complete | - |
Hope this can help you!