So far no one has mentioned this, but typically images or other uploads only exist on the original server. When lemm.ee went down, all the content those users uploaded was lost.

The text content of posts and comments is copied across all the linked servers, but the images aren't. Some instances will proxy images from a short term cache, but it's far too expensive to store the images permanently.

When a post is created, is it only stored on the original instance, or copied to every other one?

Copied

• Do all federated servers get a copy, or get posts from other server when user demands them?

They get copies of all posts from communities their users subscribe to.

• When an instance shuts down, is its content gone forever, or do other instances keep copies?

The copies remain. But new comments or posts won't federate to other copies.

• Is there any kind of “shared” storage in the Fediverse, or network that store everything?

No,

• Could one still access all lemm.ee content now? Or post in it's communities?

Yes, as long as an instance that was around long enough to federate with it still exists. You can browse from SJW for example.

please remove the AI sentence before the questions in your post

[図書館]^（としょかん）

They are sold for LLM training sets.

-Caroline deleted-

“Goodbye, Caroline…”