Creating regular persistent disk snapshots to backup data, even if they’re attached to a running instances. Snapshots are a faster, more cost-effective way to back up data versus to create a full image of a disk.
Snapshots are differential, so administrator can create regular snapshots on a persistent disk much faster and at a much lower cost. Snapshots are always created based on the last successful snapshot taken.
use the gcloud compute disks snapshot command:
gcloud compute disks snapshot [DISK_NAME]
Creating Persistent Disk Snapshots