would lan file sharing affect internet connection speed?
 

I'm currently living overseas due to my job, and the building I live in at the moment has a shared router used by everyone who lives in the building - I'd estimate a hundred or so people at various times, so obviously the connection gets a little strained. I was thinking about connecting a local server to the router for people to upload and download things to. If I do this, would the bandwidth used by people uploading to/downloading from the local server affect everyone else's internet connection?

(edited out - irrelevant reply - sorry)

and ...
 

The definitive answer is: it depends.
If you had a good high-speed switch and all of the file transfers involving this new box were internal to the network, the only traffic affected should be that of the machines doing the file transfer. Alas, reality may not match this ideal picture.
If that router has a good built-in switch and adequate processing power you will get very close tho zero impact. If it is a cheap switch, hub in disguise, or the router is underpowered, then any traffic going through will steal either processor or bandwidth from every other bit of traffic.

If you have good equipment, go for it. If you have a 'lowest bidder' landlord, perhaps you should test during off-hours before trusting that it will not be noticed. Or, if the risk is high, just forget the whole thing.

You mean some sort of cache server. That would only work if a lot of the people are actually downloading the same files. Some web page cache servers work good for companies where a common page is looked at a few thousand times a day.

Assuming it's a relatively modern router/switch, the LAN traffic should not be a problem. However, with that many people there's sure to be duplicate Internet traffic being generated. I would suggest developing a Squid proxy and having everyone setup their browser to use it so you can decrease WAN traffic.

I'm not convinced that there would be a lot of duplication these days. The vast majority of web-pages are dynamically generated, so other than graphics, each page is unique. Do you also want to be getting in to a situation where you are acting as a proxy for a building? It's one thing doing it for a company but if you are doing this for individuals then you'll have to provide support for all the platforms people are using to browse. Also, what about liability if anyones information gets compromised while passing through YOUR proxy server? Sure are hell you'll get someone whos credit card info gets compromised, it's not going to be THEIR fault, they're going to sue the guy who put a proxy server in the middle!