Experiment creating disk snapshots and deleting all but one to verify data restored for Google Cloud Platform (GCP) Compute Engine

gcp-gce-snapshots-delete-restore.sh

#!/usr/bin/env bash

#####################################################################
# REFERENCES
# - https://cloud.google.com/compute/docs/instances/create-start-instance 
# - https://cloud.google.com/compute/docs/disks/create-snapshots 
# - https://cloud.google.com/compute/docs/disks/restore-snapshot 
#####################################################################
export PROJECT_ID=$(gcloud config get-value project)
export PROJECT_USER=$(gcloud config get-value core/account) # set current user
export PROJECT_NUMBER=$(gcloud projects describe $PROJECT_ID --format="value(projectNumber)")
export IDNS=${PROJECT_ID}.svc.id.goog # workflow identity domain

export GCP_REGION="us-west4" # CHANGEME (OPT)
export GCP_ZONE="us-west4-a" # CHANGEME (OPT)
export NETWORK_NAME="default"

# enable apis
gcloud services enable compute.googleapis.com \
    storage.googleapis.com

# configure gcloud sdk
gcloud config set compute/region $GCP_REGION
gcloud config set compute/zone $GCP_ZONE


#############################################################
# NETWORKING
#############################################################
# firewall allow ssh
gcloud compute firewall-rules create fw-allow-ssh \
    --network=$NETWORK_NAME \
    --action=allow \
    --direction=ingress \
    --target-tags=allow-ssh \
    --rules=tcp:22


#############################################################
# COMPUTE
#############################################################
export INSTANCE_NAME="snapshot-test-1" # disk name should be same

# create compute instance to test from proxy-only network to ILB
gcloud compute instances create $INSTANCE_NAME \
    --machine-type e2-micro \
    --zone $GCP_ZONE \
    --network $NETWORK_NAME \
    --tags allow-ssh


#############################################################
# SNAPSHOTS
#############################################################
export IMAGE1_NAME="image1.jpg"
export IMAGE1_URL="https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/cute-cat-photos-1593441022.jpg"
export IMAGE2_NAME="image2.jpg"
export IMAGE2_URL="https://media.istockphoto.com/id/1267021092/photo/funny-winking-kitten.jpg"
export IMAGE3_NAME="image3.jpg"
export IMAGE3_URL="https://thumbs.dreamstime.com/b/portrait-funny-cat-fly-his-nose-portrait-funny-cat-fly-his-nose-isolated-white-background-125606127.jpg"

export SNAPSHOT1_NAME="snapshot1"
export SNAPSHOT2_NAME="snapshot2"
export SNAPSHOT3_NAME="snapshot3"

export DIR_NAME="cat-photos"

# create an images folder in home directory (via IAP tunnel)
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- mkdir -p $DIR_NAME

# ------- 1st image -----------

# download image1 from web using curl (via IAP tunnel)
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- curl -o $DIR_NAME/$IMAGE1_NAME $IMAGE1_URL

# verify image1 in directory
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- ls -hl $DIR_NAME

# create snapshot of disk with only image1 on disk
gcloud compute snapshots create $SNAPSHOT1_NAME \
    --source-disk $INSTANCE_NAME \
    --source-disk-zone $GCP_ZONE

# ------- 2nd image -----------

# download image2 from web using curl (via IAP tunnel)
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- curl -o $DIR_NAME/$IMAGE2_NAME $IMAGE2_URL

# verify image2 in directory
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- ls -hl $DIR_NAME

# create snapshot of disk with 2 images on disk
gcloud compute snapshots create $SNAPSHOT2_NAME \
    --source-disk $INSTANCE_NAME \
    --source-disk-zone $GCP_ZONE

# ------- 3rd image -----------

# download image3 from web using curl (via IAP tunnel)
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- curl -o $DIR_NAME/$IMAGE3_NAME $IMAGE3_URL

# verify image3 in directory
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- ls -hl $DIR_NAME

# create snapshot of disk with 3 images on disk
gcloud compute snapshots create $SNAPSHOT3_NAME \
    --source-disk $INSTANCE_NAME \
    --source-disk-zone $GCP_ZONE


#############################################################
# SNAPSHOTS TEST
#############################################################
export DISK_NAME="new-disk1"

# delete snapshots 1,2
gcloud compute snapshots delete $SNAPSHOT1_NAME
gcloud compute snapshots delete $SNAPSHOT2_NAME

# verify only snapshot3 remains
gcloud compute snapshots list

# stop instance, detach and delete disk (simulate disaster)
gcloud compute instances stop $INSTANCE_NAME --zone $GCP_ZONE
gcloud compute instances detach-disk $INSTANCE_NAME \
    --disk $INSTANCE_NAME \
    --zone $GCP_ZONE
gcloud compute disks delete $INSTANCE_NAME

# create disk from only remaining snapshot3
gcloud compute disks create $DISK_NAME \
    --size="10GB" \
    --source-snapshot=$SNAPSHOT3_NAME

# attach disk (boot) to instance and start it back up
gcloud compute instances attach-disk $INSTANCE_NAME \
    --disk $DISK_NAME \
    --boot \
    --zone $GCP_ZONE
gcloud compute instances start $INSTANCE_NAME --zone $GCP_ZONE

# verify which images are in test images folder
gcloud compute ssh $INSTANCE_NAME --zone $GCP_ZONE -- ls -hl $DIR_NAME

# remember to clean up or delete project to avoid unnecessary billing

Disk snapshot recovery experiment

Recently a customer asked whether disk snapshots were an effective means to backup their self-managed database in case of need for disaster recovery. They noticed the first snapshot was much larger than the smaller subsequent incremental snapshots, and asked whether deleting some snapshots still rebuilds the entire disk.

Experiment

• spin up compute instance
• download 1st image file and snapshot
• download 2nd image file and snapshot
• download 3rd image file and snapshot
• delete snapshots 1 and 2
• stop instance, detach disk, delete disk to simulate a disaster
• create disk from only remaining snapshot3
• attach new disk, start instance, and verify all 3 image files present

Result (success)

Note that the 2nd image was 0 bytes in size so restored disk was exact same as deleted.