Filestore: ACE Exam Study Guide (2026)

Image source: Google Cloud Documentation

Google Cloud Filestore is a managed NFS file storage service (POSIX‑compliant) designed for applications that require a shared filesystem. It is a regional resource that offers both zonal and multi-zonal availability tiers.

POSIX is a standard that ensures portability by unifying system calls, file and process handling, and permissions. Linux and macOS follow POSIX, so software written for one typically works on Filestore without modification.

1. Filestore Use Cases

• Shared storage for GKE and Compute Engine workloads.
• Content management systems (CMS) and media processing.
• Machine learning workloads needing shared datasets.
• Home directories for Linux users.
• Serverless: Cloud Run (Gen 2) can mount Filestore via Direct VPC Egress.

2. Filestore Tiers (Updated for 2026)

Tiers determine performance, availability, and capacity.

Note: You cannot change tiers in-place. You must migrate data to a new instance.

3. Networking & Connectivity

• Deployed into a VPC network via a private IP.
• Must be in the same VPC and region as clients (or connected via VPC Peering/VPN).
• Mounting:
  • GKE: Use the Filestore CSI driver for automatic provisioning.
  • Cloud Run (Gen 2): Use --add-volume=type=nfs and --vpc-egress=all-traffic.

4. Capacity & Scaling

• Increase Only: You can increase capacity, but you cannot decrease it.
• Downtime: Scaling may cause brief downtime on Basic/Zonal tiers.
• Online Scaling: The Enterprise tier supports online scaling with zero downtime, making it the preferred choice for mission-critical GKE applications.
• Independent Scaling: The Zonal tier allows scaling performance and capacity independently.

5. Data Protection: Backups & Snapshots

Understanding the difference is critical for disaster recovery (DR).

Filestore Backups

• What: A point-in-time copy of the entire share, stored separately from the instance.
• Scope: Can be stored in the same region or different regions (Multi-regional).
• Restore: You MUST restore a backup to a new Filestore instance. You cannot restore in-place.
• Use Case: Disaster recovery or moving data to a new region/tier.

Filestore Snapshots

• What: Fast, local point-in-time copies of the filesystem.
• Availability: Supported on Enterprise, Zonal, and Regional tiers.
• Restore: Allows for quick recovery of individual files or the entire share.
• Use Case: Protecting against accidental deletions or rolling back local changes.

6. Security

• IAM: Controls instance management (create, delete, backup).
• POSIX/NFS: Controls file-level access (UID/GID, read/write permissions).
• Network: Isolated within your VPC; supports CMEK on Enterprise tiers.

Important: IAM does NOT control who can read or write individual files inside the share; that is handled by NFS permissions.

7. Using in a Spring Boot App (Example)

Filestore is mounted as a local directory. Use the java.nio.file API.

@Service
public class FileService {

    private final Path mountPoint = Paths.get("/mnt/filestore/data");

    public void save(String fileName, byte[] content) throws IOException {
        Files.write(mountPoint.resolve(fileName), content);
    }
}

8. Common ACE Exam Scenarios

• Scenario: Shared POSIX for GKE? → Filestore.
• Scenario: Many small (10GB) shares for GKE pods? → Filestore Enterprise (Multishares).
• Scenario: Mount shared storage to Cloud Run? → Filestore + Direct VPC Egress.
• Scenario: Scale performance and capacity independently? → Zonal tier.
• Scenario: In-place tier upgrade? → Not possible (must create new and migrate).
• Scenario: Regional High Availability (99.99% SLA)? → Regional or Enterprise tier.
• Scenario: Global object storage? → Cloud Storage (not Filestore).

9. Quick Summary Table

Note: Multi-writer PD exists but is highly specialized (Block storage).

10. External Links

• Youtube - Andrew Brown - GCP ACE
• Firestore - The Cloud Girl
• Which Storage Should I Use - The Cloud Girl
• What are different storage types - The Cloud Girl