I am looking at getting a TrueNAS setup which will have 2.5GbE. I'll be connecting this NAS via a standard 1GbE switch (CAT6 cable). My ASUS router has a 2.5GbE port. Most of my other devices such as computers, TVs and media boxes support 1GbE and are all maxing out at 1.0Gbps, except for one computer which supports 2.5Gbps. All of these devices are connecting back to the router via the same standard 1GbE switch.
I am going to be running Jellyfin Server on the NAS and all my TVs, media boxes and mobile devices will connect back to this NAS via Jellyfin client for video content. There will be times when multiple devices will access video content simultaneously. Is it worth upgrading my network switch to 2.5GbE and connecting this switch to my router's 2.5GbE port? This will mean connectivity between the Jellyfin Server and the router will be at 2.5Gbps. I was thinking this will help with the multiple incoming connections to the Jellyfin Server even thought the devices accessing the Jellyfin Server would be maxing out at 1.0Gbps, except for that one PC which supports 2.5Gbps. Should I invest in that 2.5GbE switch or will it not make any difference?
You could invest in 2.5GbE if you constantly transfer files between your multiple devices and the Truenas server over ethernet.
For Jellyfin even with multiple 4K streams its not going to saturate 1GbE.
1 giga bit = 1000 Mega bit. Assuming that an ultra high quality 4K stream will be 100 Mega bit (Very unlikely), you could theoratically run 10 4K streams.
Just for jellyfin, no point in updating to 2.5GbE.