How are mounts in sized?

Is everything OK as long as the total size of the mounts is less than the value in the disk directive?

Mount sizes are defined with the disk key in your configuration file.

Mounts are entirely optional - it may not be necessary for your application to have write access. If not, you will still need to define the disk key in to the minimum requirements

disk: 256

disk defines the size of the persistent disk of the application (in MB), and you will receive a validation error if you attempt to set it lower than 256MB.

Once your mounts are defined with the disk key, all mounts will share the amount of disk you allocate to them.

For example, in a file that configures its mounts with

disk: 1024

        source: local
        source_path: private
        source: local
        source_path: uploads

The mounts at mnt/private and mnt/uploads will be accessible in the /app directory at private and web/uploads, and they will together share a maximum of 1024 MB.

If you go over that total amount between them, then you will need to expand this pre-allocated disk space in the disk key.

You can observe the disk space used by each application mount using the CLI:

$ platform mount:size