Persistent volumes

Persistent volumes

By default, a service's filesystem is ephemeral: every redeploy starts fresh from the image, and any file written at runtime disappears. A persistent volume attaches a durable directory that survives redeploys and restarts.

Adding a volume

In the service panel, Volumes tab:

1. Mount path: the directory seen by your application (e.g. /app/uploads).
2. Size: in GiB, based on your needs and your plan's limits.

The volume is provisioned and mounted on the container's next startup. Everything your application writes under this path is preserved.

Use cases

// The application simply writes to the mounted path
await fs.promises.writeFile("/app/uploads/avatar-42.png", buffer);

What you need to know

• The rest of the filesystem stays ephemeral: only mounted paths persist. Don't rely on anything else.
• Volume and scaling: a volume is attached to one instance. If you plan to move to multiple replicas, prefer shared storage (database, object storage) for data accessed by all instances.
• Size is chosen at creation time. Allow a bit of margin.
• Deletion: deleting a volume permanently erases its content. Export whatever needs to be kept first (via the web terminal, for example).

Databases

Database-type services (PostgreSQL, MySQL…) are already backed by a platform-managed persistent volume: nothing to configure, your data natively survives restarts.