Can someone explain to me how I can calculate the maximun
number of servers that a T1 leased line (1,54Mbps) can host, if we say that every server will have 30GB bandwidth? Thank you.

well there's no simple equation you can use because it determins on lots of variables (peak times of access, type of sites, etc, etc)...

but i'd gather to say probabbly 5-6 maybe 8 max.

5 would be a safe number. actuallyi wouldnbt even put more then 5 on a single t1.

Only 5 servers in a T1? I'm trying to find out how can a dedicated server hosting company be profitable. For example, a company which offers servers for $100-$120/month. Can this company be profitable?

You basically need to figure you can't do more than 50% of max bandwidth when calculating bandwidth on capped lines. This is because the traffic of servers generally tend to peak at the same time. So even though you may only be doing 250kbps normally, you may being peaking to 1400kbps and not be able to handle anymore servers. A full T1 at sustained full usage is around 450GB of bandwidth. So the most actual usage you'd be able to get is around 200GB.

Hope that helps (and makes some sense).

It does depend on many things, but, judge for yourself, I used to work at an ISP, we had two T-1s, spoke BGP, here is what we had.

196 dialup lines
three name servers
7 NT servers about 400 clients total on them
15 linux/hosting servers mail server, tucows mirrors, and hosting about another 800 clients on that.
about 25 colos or so.

A T-1 can send data both ways at ~1.544Mpbs with little to no degradation. It is true around 70% if you are growing you need to think about upgrading, but even at 90% your clients should not notice a big problem sending or receiving data.

Disclaimer: Again, we did not host huge hit sites, we had like 5 sites that got about 1million hits a month, doverdowns.com, corpamerica.com, delaware.com and .net and lawservice.com, we had a few that was about 100k or so a month, the rest were just normal local websites...maybe 10k hits if they were lucky. We did no porn at all, but of course ymmv.