Persistent Disk
Google Persistent Disk is a part of the GCP block storage.
To encrypt a persistent disk, in a specific GCP project, in a specific region, using a specific encryption key:
gcloud compute disks \
create encrypted-disk \
--kms-key \ projects/[KMS_PROJECT_ID]/locations/[REGION]/
keyRings/[KEY_RING]/cryptoKeys/[KEY]
Best practices
Encrypt both the OS and data volumes.
Encrypt each data volume at creation time.
Encrypt the machine instance snapshots.
For highly sensitive environments, encrypt persistent disks using a CMK inside Google Cloud KMS.
Set names for Google’s persistent disks to allow you to have a better understanding of which persistent disk belongs to which machine instance.
Use tagging (labelling) for persistent disks or snapshots for a better understanding of which disk or snapshot belongs to which machine instance.