Hello,

I've been running an old laptop as a server (with debian for Jellyfin + Pi-hole) for some time now with an external HDD (usb3). I just managed to get ahold of another one and I was thinking to expand my setup creating somewhat of a cluster, allowing more connexion (sharing Jellyfin with relative) and adding some app (NextCloud, Home assistant, ...).

First thing first, I'm a bit lost on how to effectively connect two laptop for that. I've looked around a bit, and heard about load of thing, mainly Proxmox, Dockers, K3s, ... I don't think Proxmox would be the right choice for me (not really a use for virtualization, don't have to much performance on the hardware side, already used to debian + Docker (for other projects)), but is really K3s the way to go? If that's the case, do you have any tutorial/documentation to recommend to get started? I'm also open to other alternative.

Second part, data, more specifically how to share actual file between the laptop and backup. As my setup had only media file, I never really gave backup a thought. I know about the 3-2-1, and I was thinking to add another HDD to the second laptop (which would also help with the sharing part), replicating data from the first drive as a mirror as well as having a third copy by some family member. Is this really a good idea and how to do that? I've read about Ceph or GlusterFS, but they need 3 nodes. As for a NAS, it would require actually buying hardware I'm not sure I really need. I know I could simply share the actual hdd with nfs or something like that, but I was wondering if that could cause a bottleneck, the first laptop having to do all the r/w on the disk. Any recommendation on that side, or on how to backup to another house as well?

Lastly, security, because right now my server is only on my local network (for Jellyfin) and I know I'll need to think in depth about that. Any recommendation on were to start?

Thank you in advance!