Do I need persistent storage for containers if the app writes files?

Yes — if the app writes files that need to survive container restarts or recreation, you should use persistent storage.

Why

Container filesystems are usually ephemeral:

• If the container stops, is deleted, or rescheduled, its writable layer is often lost.
• Any files written inside the container may disappear unless they’re stored on a mounted volume or external storage.

Use persistent storage when:

• The app saves user uploads
• It writes logs you need to keep
• It creates cache/data files that must survive restarts
• It stores databases inside the container

You may not need it when:

• The files are temporary
• The app can regenerate them on startup
• Data is stored in an external service like:
  • object storage (S3, GCS, Azure Blob)
  • managed database
  • network file share

Common options

• Docker volume / bind mount for local or single-host setups
• Kubernetes PersistentVolume / PersistentVolumeClaim for clusters
• Cloud storage / managed disk for production

Rule of thumb

If losing the file would be a problem, mount persistent storage.
If the file is disposable, you can keep it inside the container.

If you want, I can help you decide for a specific app stack (e.g. Node.js, Python, database, uploads, logs).