Nextcloud Server and External Storage Data Transfer Mechanism

Hi Everyone,

I am trying to understand the data transfer mechanism from the nextcloud server to the external storage mounted on the nextcloud server.

I wanted to know if the file uploaded by the user to the folder pointing to the external storage in the nextcloud server will be directly uploaded from the nextcloud server to the external storage, or else does this involve any of the redundant transfers between the client machine and again and then get transferred to the external storage mounted in the nextcloud.

Here is the basic diagram to get the picture.

Please help me out on understanding the mechanism involved in the backend for data transfer of files between the client machine, Nextcloud server and the external storage.

Regards
Karan