A Zonal Persistent Disk is a durable, high-performance block storage option in Google Cloud Platform that is attached to virtual machine (VM) instances within a single zone. These disks are fundamental to running workloads on Compute Engine and provide reliable storage that persists independently o…A Zonal Persistent Disk is a durable, high-performance block storage option in Google Cloud Platform that is attached to virtual machine (VM) instances within a single zone. These disks are fundamental to running workloads on Compute Engine and provide reliable storage that persists independently of VM lifecycle.
Key characteristics of Zonal Persistent Disks include:
**Durability and Availability**: Data is automatically replicated within the zone to protect against hardware failures. However, since the disk exists in a single zone, it is not protected against zonal outages.
**Disk Types**: GCP offers several persistent disk types:
- Standard persistent disks (pd-standard): HDD-backed, cost-effective for sequential read/write operations
- Balanced persistent disks (pd-balanced): SSD-backed with balanced price and performance
- SSD persistent disks (pd-ssd): Highest performance for random IOPS-intensive workloads
- Extreme persistent disks: Maximum IOPS and throughput for demanding applications
**Flexibility**: You can resize disks while they are attached to running VMs, and you can create snapshots for backup and disaster recovery purposes. Snapshots can be used to create new disks in different zones or regions.
**Attachment Options**: A zonal persistent disk can be attached to multiple VMs in read-only mode, or to a single VM in read-write mode. This enables scenarios where multiple instances need to access the same data.
**Use Cases**: Ideal for databases, application data storage, boot disks, and any workload requiring persistent block storage within a single zone.
**Considerations for Cloud Engineers**: When planning solutions, consider that zonal persistent disks do not provide redundancy across zones. For higher availability requirements, you should implement Regional Persistent Disks, which replicate data across two zones within a region, or use snapshot-based backup strategies to protect critical data.
Zonal Persistent Disks are fundamental storage components in Google Cloud Platform. They provide durable, high-performance block storage for Compute Engine virtual machines. Understanding zonal persistent disks is essential because they are the default and most commonly used storage option for VM instances, making them a frequent topic in the certification exam.
What is a Zonal Persistent Disk?
A Zonal Persistent Disk is a network-attached block storage device that exists within a single zone. Key characteristics include:
• Zone-specific: The disk resides in one specific zone and can only be attached to VM instances in that same zone • Durability: Data is automatically replicated within the zone for redundancy • Independence: Disk lifecycle is separate from VM lifecycle - data persists even after VM deletion • Types available: Standard (HDD), Balanced (SSD), SSD, and Extreme persistent disks
How Zonal Persistent Disks Work
1. Attachment: Disks attach to VMs via the network, not physical connection 2. Replication: Data is replicated across multiple physical disks within the zone 3. Snapshots: You can create snapshots for backup, which are stored in Cloud Storage across multiple regions 4. Resizing: Disks can be resized while attached to a running VM (increase only) 5. Multiple attachment: Can be attached to multiple VMs in read-only mode, or single VM in read-write mode
Key Limitations
• Cannot span multiple zones - this is the primary constraint • If the zone experiences an outage, the disk becomes unavailable • Cannot be attached to VMs in different zones
Exam Tips: Answering Questions on Zonal Persistent Disk
Tip 1: When a question mentions high availability across zones, zonal persistent disk is NOT the answer - look for Regional Persistent Disk instead.
Tip 2: If a scenario requires the lowest cost storage option, Standard (HDD) zonal persistent disk is typically the answer.
Tip 3: Questions about attaching a disk to VMs in different zones indicate you need snapshots to create a new disk in the target zone.
Tip 4: For scenarios requiring shared read-only access among multiple VMs, remember that zonal persistent disks support multi-reader mode.
Tip 5: When exam questions mention data persistence after VM termination, persistent disks are the correct choice over local SSDs.
Tip 6: Performance-related questions: SSD persistent disks offer higher IOPS than standard persistent disks. Extreme persistent disks provide the highest performance but at premium cost.
Tip 7: Watch for questions about disk snapshots - they are globally available and can be used to create disks in any region, providing a migration path between zones.