💾 Google Cloud Persistent Disks – Reliable Block Storage for VMs

When running virtual machines (VMs) in Google Cloud, having reliable and high-performance storage is crucial. Google Cloud Persistent Disks (PDs) provide durable block storage for Compute Engine VMs. Unlike object storage like Cloud Storage, Persistent Disks function like traditional hard drives attached to your VMs, supporting operating systems, applications, and databases.

Persistent Disks are essential for workloads that require low latency, consistent IOPS, and persistence across VM restarts. This makes them ideal for databases, transactional systems, and enterprise applications.

This guide will explore:

• What Persistent Disks are
• Types and features
• 3 practical examples
• Interview and exam memory tips
• Importance for cloud professionals

🔎 What Are Persistent Disks?

Persistent Disks (PDs) are durable block storage volumes in GCP. They persist independently of VM lifecycles, meaning your data remains intact even if the VM is stopped or deleted.

Key Concepts

1. Block Storage: Data is stored in fixed-size blocks, allowing fast read/write operations.
2. Attachment Modes: Can be read/write attached to one VM or read-only attached to multiple VMs.
3. Durability: Data is replicated within a zone to prevent loss.
4. Scalability: Supports large volumes (up to 64 TB per disk) and high IOPS.

⚙️ Persistent Disk Types

🛠️ Example Programs

✅ Example 1: Creating a Persistent Disk via gcloud CLI

gcloud compute disks create my-disk \
    --size=200GB \
    --type=pd-ssd \
    --zone=us-central1-a

Use Case: Attaching high-performance storage to a VM hosting a database.

✅ Example 2: Attaching Persistent Disk to a VM

gcloud compute instances attach-disk my-vm \
    --disk=my-disk \
    --zone=us-central1-a

Use Case: Ensure VM has persistent storage even after reboots or maintenance.

✅ Example 3: Mounting Persistent Disk in Linux VM

sudo mkfs.ext4 -F /dev/sdb
sudo mkdir /mnt/data
sudo mount /dev/sdb /mnt/data

Use Case: Format and mount the disk for application data storage, logs, or backups.

⚡ Core Features

1. Persistence Across VM Lifecycles: Data remains intact after stopping or deleting VMs.
2. Automatic Replication: Zonal disks are replicated within the same zone; regional disks replicate across zones.
3. Snapshot & Restore: Create snapshots for backup or cloning disks.
4. Resize Dynamically: Expand disk size without downtime.
5. Encryption: Data is encrypted at rest and in transit automatically.

🧠 Tips to Remember for Exams & Interviews

1. Acronym – “PADS”:

   • Persistence
   • Attachment to VM
   • Durability via replication
   • Snapshots and scaling

2. Analogy: Think of Persistent Disks like external SSDs connected to your cloud VM, which keep your data safe even if the VM is turned off.

3. Key Memory Sentence:

“Persistent Disks provide durable, block-level storage that stays intact across VM lifecycles and supports snapshots and high IOPS workloads.”

🎯 Why Learn Persistent Disks?

1. Enterprise Applications: Supports databases, ERP systems, and high-transaction workloads.
2. Cost & Performance Optimization: Understand disk types to balance cost vs performance.
3. Cloud Exams: Appears in Google Cloud Associate and Professional exams.
4. Integration with Other Services: Works with Compute Engine, GKE, BigQuery for VM storage requirements.

🔒 Best Practices

1. Choose Disk Type Wisely: Align type (Standard, Balanced, SSD, Extreme) with workload needs.
2. Use Snapshots: Regular backups ensure disaster recovery.
3. Encrypt Sensitive Data: GCP handles encryption, but customer-managed keys provide extra control.
4. Monitor Disk Metrics: Use Cloud Monitoring for IOPS, throughput, and latency.
5. Regional Disks for High Availability: Protect data against zone-level failures.

📘 Conclusion

Google Cloud Persistent Disks are the reliable backbone for VM storage, offering durability, scalability, and flexibility. They are essential for workloads requiring high performance, consistent access, and durability. By understanding disk types, attachment modes, snapshots, and encryption, you can architect robust cloud applications.

For exam preparation, remember PADS – Persistence, Attachment, Durability, Snapshots – and practice creating, attaching, and mounting disks using gcloud CLI or SDKs. Mastering Persistent Disks gives a strong foundation for other GCP storage and compute services.