Help Center/ Elastic Volume Service/ User Guide (Kuala Lumpur Region)/ Managing Encrypted EVS Disks
Updated on 2025-03-10 GMT+08:00
View PDF
Share

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.

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

Keys provided by KMS include a Default Master Key and Customer Master Keys (CMKs).
  • Default Master Key: A key that is automatically created by EVS through KMS and named evs/default.

    It cannot be disabled and does not support scheduled deletion.

  • CMKs: Keys created by users. You can use existing keys or create new ones to encrypt disks. For details, see "Key Management Service" > "Creating a CMK" in the Data Encryption Workshop User Guide.

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.

If you use a CMK to encrypt disks and this CMK is then disabled or scheduled for deletion, data cannot be read from or written to these disks or may never be restored. See Table 1 for more information.
Table 1 Impact of CMK unavailability

CMK Status

Impact

How to Restore

Disabled
  • For an encrypted disk already attached: Reads and writes to the disk are normal. If the disk is detached, it cannot be attached again.
  • For an encrypted disk not attached: The disk cannot be attached anymore.

Enable the CMK. For details, see "Managing CMKs" > "Enabling One or More CMKs" in the Data Encryption Workshop User Guide.

Scheduled deletion

Cancel the scheduled deletion for the CMK. For details, see "Managing CMKs" > "Canceling the Scheduled Deletion of One or More CMKs" in the Data Encryption Workshop User Guide.

Deleted

Data on the disks can never be restored.

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 Relationship between encrypted images and system disk encryption

    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 3 Relationship between backups, snapshots, images, and data disk encryption

    Disk Created On

    Method of Creation

    Whether Data Disk Will Be 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

Table 4 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 EVS Administrator permissions to EVS. Then, the user can create and obtain keys to encrypt and decrypt disks.
  • 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 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.