External storage question - what is the behavior of server and clients if storage is unavailable?

Tl;dr - when an external storage becomes temporarily unavailable, what is the behavior of sync clients for new files and existing files? Is there a time limit on how long an external storage can be unavailable?

I have a Nextcloud server that my family uses to sync files. I have a dedicated server in a data center that runs the instance but I don’t want to keep all the nextcloud data for the following reasons:

  1. space constraints on the hosted server
  2. performance of uploading/download large files that change frequently (this is only an issue for my account)

As such, I would like to set up an external storage system on a local machine to handle archives and cold storage as well as allow me to make frequent changes to those large files I spoke of. I’ve read the setup documentation and have gotten an external storage working for a test.

However, I don’t see anything in the documentation about what happens if an external storage becomes unavailable. Since the external storage will be remote to the main server, there is virtual certainty that connectivity or other issues will at some point interrupt the connection between the two. I don’t want sync clients to delete files just because an external storage is missing. I don’t want the web service to become totally unresponsive or grind to a halt. Since I intend to store work files on the external storage, I want to make sure I understand the implications of this before committing to it. Thanks for your help!