Encryption Scenarios

System disk encryption

System disks are created along with servers and cannot be created separately. So whether a system disk is encrypted or not depends on the image selected during the server creation. See the following table for details.

**Table 1** Encryption relationship between images and system disks
Creating Server Using Encrypted Image	Whether System Disk Will Be Encrypted	Description
Yes	Yes	For details, see Managing Private Images > Encrypting Images in the Image Management Service User Guide.
No	No	-

Data disk encryption

Data disks can be created along with servers or separately. Whether data disks are encrypted depends on their data sources. See the following table for details.

**Table 2** Encryption relationship between backups, snapshots, images, and data disks
Created On	Method of Creation	Whether Data Disk Will Be Encrypted	Description
The ECS console	Created together with the server	Yes/No	When a data disk is created together with a server, you can choose to encrypt the disk or not. For details, see Getting Started > Creating an ECS > Step 1: Configure Basic Settings in the Elastic Cloud Server User Guide.
The EVS console	No data source selected	Yes/No	When an empty disk is created, you can choose whether to encrypt the disk or not. The encryption attribute of the disk cannot be changed after the disk has been created.
	Creating from a backup	Yes/No	When a disk is created from a backup, you can choose whether to encrypt the disk or not. The encryption attributes of the disk and backup do not need to be the same. When you create a backup for a system or data disk, the encryption attribute of the backup will be the same as that of the disk.
	Creating from a snapshot (The snapshot's source disk is encrypted.)	Yes	A snapshot created from an encrypted disk is also encrypted.
	Creating from a snapshot (The snapshot's source disk is not encrypted.)	No	A snapshot created from a non-encrypted disk is not encrypted.
	Creating from an image (The image's source disk is encrypted.)	Yes	-
	Creating from an image (The image's source disk is not encrypted.)	No	-

Constraints

**Table 3** Constraints on disk encryption
Item	Description
Types of disks supporting encryption	All disk types
Constraints on encrypted disks	The encryption attribute of a disk cannot be changed after the disk is created, meaning that: An encrypted disk cannot be changed to a non-encrypted disk. A non-encrypted disk cannot be changed to an encrypted disk.
Constraints on user permissions	When a user uses the encryption function, the condition varies depending on whether the user is the first one ever in the current region or project to use this function. If the user is the first user, the user needs to follow the prompt to create an agency, which grants KMS Administrator permissions to EVS. Then the user can create and obtain keys to encrypt and decrypt disks. NOTE: The first user must have the KMS Administrator permissions to create the agency. If the user does not have the KMS Administrator permissions, contact the account administrator to grant the permissions first. If the user is not the first user, the user can use encryption directly.
Constraints on encrypted images	Encrypted images cannot be replicated across regions. Encrypted images cannot be changed to non-encrypted images. Encrypted images cannot be exported.

Creating an Encrypted EVS Disk

Before you use the encryption function, KMS access rights need to be granted to EVS. If you have the Security Administrator permissions, grant the KMS access rights to EVS directly. If you do not have this permission, contact a user with the security administrator permissions to grant KMS access rights to EVS and then select the encryption option to create an encrypted disk.

For details about how to create an encrypted disk, see Create an EVS Disk.

Detaching an Encrypted EVS Disk

Before you detach a disk encrypted by a CMK, check whether the CMK is disabled or scheduled for deletion.

If the CMK is available, the disk can be detached and re-attached, and data on the disk will not be lost.
If the CMK is unavailable, the disk can still be used, but there is no guarantee for how long it will be usable. If the disk is detached, it will be impossible to re-attach it later. In this case, do not detach the disk without a working CMK.

The restoration method varies depending on the CMK status. For details, see EVS Encryption.

For details about how to detach an encrypted disk, see Detaching a Data Disk.

Managing Encrypted EVS Disks

Encryption Scenarios

Constraints

Creating an Encrypted EVS Disk

Detaching an Encrypted EVS Disk