this post was submitted on 09 Jul 2023
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Edit: I am partially wrong. (See below)
They're stored on their host Instance. Only text is copied across instances.
That is not true. As long as a user on your instance is subscribed to a community, the media content of posts [Edit: only posts linking to outside sources, e.g imgur] of that community is stored locally on your instance as well.
This, of course, only applies to media which is uploaded to Lemmy, links to media hosted externally are not downloaded.
See this issue for more context.
Edit: I want to clarify that I was partially wrong - Lemmy only locally caches content which is hosted on outside sites. It does (should?) not cache content that was directly uploaded to a Lemmy instance and just embeds the source media.
I think this could be a ticking DOS time bomb.
Someone manages to spam upload massive files to the largest Lemmy instances could wipe out a ton of smaller ones.
Not to mention scalability wise this seems like a nightmare… eventually the largest Lemmy instances will have petabytes of media data with 100s of gbs coming in per day, giving other instances no chance to sync with them.
I think the system architecture needs a significant review. This won’t scale.
I agree. It's also a tremendous waste of resources. I'm all for redundancy (like CDNs), but this seems incredibly poorly thought out. If Lemmy (as a whole) every scales to the size of other social media, the space requirements will start to become unreasonable.
Why wouldn't something like symlinks be implemented? Not saying specifically use symlinks, but there has to be a similar, better way.
The obvious way would be to just not cache content locally and always link to the source instance. While this would concentrate the strain immensely, it would also greatly decrease the storage space used by all other instances.
There might also be other viable alternatives such as using a CDN and having it selectively cache content which is requested often etc.
~~As of now, Lemmy does not support either, though. ~~
Edit: I want to clarify that I was partially wrong - Lemmy only locally caches content which is hosted on outside sites. It does (should?) not cache content that was directly uploaded to a Lemmy instance and just embeds the source media.