Hello there, I'm in this rabbit hole of self hosting, but it's just for me and my wife, mostly for me though.
I've put together on a broken laptop of 10yo, Ubuntu server 500gb (motherboard) + 2TB storage (DVD tray), CasaOS, Nextcloud, Immich and Plex.
I have a total of 300gb of photos and videos (including immich dB) , 50Gb of docs (including nextcloud dB), and everything else is disposable, like some movies.
I do not plan to have extra services, maybe a password manager.
In this black Friday I'll buy a mini pc i5 and another 2TB drive to store zipped/encrypted backup files. And will most likely try proxmox there.
Now to the point, I'm seeing a lot people doing NAS separately, and some even putting things like Plex on the NAS server and not on the "main server". And the question is, don't I already have a NAS? My Ubuntu is sharing 2TB through the network, I'm configuring backups (with duplicati). What would I really gain if I buy a cheap synology NAS only for a shared folder? The mini pc I'll buy with i5 16gb won't do a better job than a cheap 1ghz 2mb memory NAS?
I hope I make sense, thanks in advance.
I mean, a NAS is literally Network Attached Storage. Your old laptop has storage and, presumably, is on the network; that's a NAS.
The reason why people have standalone NAS boxes is because a laptop usually can't hold all that much in the way of storage. My NAS has 42 TB of addressable storage; that's not really viable on a laptop. Add in any form of redundancy (my 42 TB of storage comes from five hard drives), caching (32 GB of RAM helping with a read cache), or other services and people quickly outgrow a laptop or even a miniPC.
I'm generally of the camp that only have storage and storage-based services on my NAS, so the CPU of my NAS is super weak compared to my actual home server. There is a good chance the CPU in your laptop might be stronger than my NAS's CPU even. Other people combine their NAS with their home server, needing a stronger CPU as a result.
As for why a prebuilt? Some people don't want to delve into that and just want Storage That Works (tm). I don't dive into networking content all that much, hence a prebuilt router instead of something using opnSense or something. I'm happy playing around in the guts of a storage box (it really isn't all that complicated), so I roll my own.