Part-24: 🚀Google Compute Engine Persistent Disks (PD) Explained

#gcp #googlecloud #devops #tutorial

When working with Google Compute Engine (GCE), storage plays a critical role in performance, durability, and availability of your applications. One of the most commonly used storage types in GCP is the Persistent Disk (PD).

This post will walk you through Zonal Persistent Disks and Regional Persistent Disks, their features, and when to use each.

🗂️ What are Persistent Disks?

Persistent Disks are network-attached block storage that can be attached to VM instances in Google Cloud. Unlike local SSDs, PDs are independent of the VM lifecycle – meaning data remains intact even if a VM is stopped or deleted.

PDs can be used as:

Boot Disks – To run your operating system.
Data Disks – To store application and user data.

🔑 Key Features of Persistent Disks

1️⃣ Zonal Persistent Disk

Data replicated in a single zone.
Lifecycle is not tied to the VM instance – you can attach/detach it between instances.
Provides flexibility: you can increase disk size whenever required.
Performance scales with disk size (larger disks = higher throughput and IOPS).
Can be resized at any time (but only increased, not reduced).

👉 Use case: Standard workloads that need durable storage within one zone.

2️⃣ Regional Persistent Disk

Data replicated in two zones within the same region for high availability.
Lifecycle is not tied to the VM instance – you can attach/detach it between instances.
More durable compared to Zonal PD.
Also independent of VM lifecycle.
Suitable for production workloads needing zone-level redundancy.

👉 Use case: High availability applications where resilience against a single zone failure is required.

⚡ Flexibility & Resizing

You can resize persistent disks anytime, even when attached to a running VM.
Only expansion is supported (cannot shrink the size).
For higher performance → either increase the disk size or attach additional disks.

How regional persistent disks are different from Zonal persistent disks ?

You can attach regional PDs only to VMs that use E2, N1, N2 and N2D machine types
You can't use a regional persistent disk with a memory-optimized, compute-optimized, storage-optimized or accelerator-optimized machine type VM.
You cannot use regional persistent disks as boot disks.
You can create a regional persistent disk from a snapshot but not an image.
The minimum size of a regional standard persistent disk is 200 GB.

🔑 Persistent Disk Types

Google Cloud provides 5 main types of persistent disks:

Standard Persistent Disk (pd-standard)

Backed by HDD.
Cost-effective.
Best for sequential I/O workloads like logging and backup.

Balanced Persistent Disk (pd-balanced)

Default option for most workloads.
Offers balance between cost and performance.
Great for general-purpose applications.

SSD Persistent Disk (pd-ssd)

High performance, low latency.
Better suited for applications requiring fast random access (databases, analytics).

Extreme Persistent Disk (pd-extreme)

Ultra-high performance.
Allows you to configure IOPS and throughput independently of disk size.
Ideal for mission-critical enterprise applications.

Hyperdisk (Next-gen persistent disk)

Available in three flavors:

Hyperdisk Balanced
Hyperdisk Extreme
Hyperdisk Throughput

Delivers more flexibility and performance tuning for modern workloads.

⚠️ Limitation: Hyperdisk cannot be used as a VM boot disk. It is only for data disks.

💻 Boot Disks vs Data Disks

Boot Disks (OS Disks):

Can be Standard, Balanced, SSD, or Extreme PDs.
Hyperdisk is not supported for boot disks.

Data Disks:

All Persistent Disk types including Hyperdisk can be used.
Perfect for application data, databases, analytics workloads, and throughput-intensive tasks.

How many ways we can create the Persistent Disks ?

Create Persistent Disks with source as