Latchu@DevOps

Posted on Aug 26

Part-26: Create a Regional Persistent Disk and associate to multiple VM in Google Cloud Platform (GCP)

#googlecloud #devops #virtualmachine #tutorial

In this guide, we’ll explore Regional Persistent Disks (RPDs) in Google Cloud:

✅ Understand why Regional Disks matter

✅ Create a Regional Persistent Disk

✅ Attach it to multiple VMs in Read-Only Mode

✅ See how GCP prevents Read-Write conflicts

✅ Cleanup resources to avoid charges

🔹 Step 01: Introduction

Persistent disks in GCP are:

Zonal by default → live in a single zone.
Regional when you need higher availability → automatically replicated across two zones in the same region.

Why use Regional Disks?

Protect against zonal failures.
Use them for read-heavy workloads across multiple VMs.
Ideal for high availability databases and disaster recovery.

🔹 Step 02: Create Regional Persistent Disk

👉 Navigate in console:

Compute Engine → Storage → Disks → Create Disk

Name: regional-disk1

Description: regional-disk1

Location: Regional

Region: us-central1
Primary Zone: us-central1-a
Replica Zone: us-central1-f

Type: Balanced Persistent Disk (pd-balanced)

Size: 20 GB

Labels: environment=dev

Encryption: Google-managed key

Click Create

📌 Equivalent CLI:

gcloud compute disks create regional-disk2 \
    --project=gcpdemos \
    --type=pd-balanced \
    --description=regional-disk2 \
    --size=200GB \
    --region=us-central1 \
    --replica-zones=projects/gcplearn9/zones/us-central1-a,projects/gcplearn9/zones/us-central1-f

🔹 Step 03: Review Disk Properties

Go to Compute Engine → Storage → Disks → regional-disk1

Confirm:

Type → Regional Persistent Disk
Zones → Two zones listed (us-central1-a, us-central1-b)

🔹 Step 04: Create VM Instances

# Create VM1 in us-central1-a
gcloud compute instances create vm1 \
  --zone=us-central1-a \
  --machine-type=e2-micro \
  --network-interface=subnet=default 

# Create VM2 in us-central1-a
gcloud compute instances create vm2 \
  --zone=us-central1-a \
  --machine-type=e2-micro \
  --network-interface=subnet=default

🔹 Step 05: Attach Regional Disk to VM1

Go to Compute Engine → VM Instances → vm1 → Edit
Scroll to Additional disks
Select Attach existing disk → Choose regional-disk1
Mode: Read-Only
Deletion rule: Keep disk
Save changes

🔹 Step 06: Attach Regional Disk to VM2

Repeat the same process for vm2.
Attach the same regional-disk1.
Mode: Read-Only

⚠️ Key Observation:

If you try to mount in Read-Write mode on multiple VMs, GCP will block it with an error. This prevents data corruption.

👉 Regional Persistent Disks are:

Multi-attach (Read-only) across VMs.
Single-attach (Read-write) to only one VM at a time.

🔹 Step 07: Cleanup

# Delete VM Instances
gcloud compute instances delete vm1 --zone us-central1-a
gcloud compute instances delete vm2 --zone us-central1-a

# Delete Regional Persistent Disks
gcloud compute disks delete regional-disk1 --region us-central1
gcloud compute disks delete regional-disk2 --region us-central1

🔹 Final Notes

Regional Persistent Disks improve resiliency by replicating across zones.
They can be attached in Read-only mode to multiple VMs.
Always consider application-level consistency (like clustering or DB replication) when using shared disks.

With this, you now know how to create, attach, and manage Regional Persistent Disks in GCP 🚀

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