Managing Encrypted EVS Disks

What Is EVS Disk Encryption?

EVS enables you to encrypt data on newly created disks as required. Keys used to encrypt EVS disks are provided by the Key Management Service (KMS) of Data Encryption Workshop (DEW), which is secure and convenient. You do not need to establish and maintain the key management infrastructure.

NOTICE:

The encryption attribute of a disk cannot be changed after the disk is created.

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

Keys Used for EVS Encryption

When an encrypted disk is attached, EVS accesses KMS, and KMS sends the data key (DK) to the host memory for use. The disk uses the DK plaintext to encrypt and decrypt disk I/Os. The DK plaintext is only stored in the memory of the host housing the ECS and is not stored persistently on the media. If a CMK is disabled or deleted in KMS, the disk encrypted using this CMK can still use the DK plaintext stored in the host memory. If this disk is later detached, the DK plaintext will be deleted from the memory, and data can no longer be read from or written to the disk. Before you re-attach this encrypted disk, ensure that the CMK is enabled.

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 you select when creating the server.

  Table 2 Encryption relationship between images and system disks

  Creating Server Using Encrypted Image	Whether System Disk Is Encrypted	Description
  Yes	Yes	For details, see Managing Private Images > Creating Encrypted 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 3 Encryption relationship between backups, snapshots, images, and data disks

  Disk Created On	Method of Creation	Whether Data Disk Is Encrypted	Description
  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.
  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	-

Notes and Constraints

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 Creating 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 Keys Used for EVS Encryption.

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