Does anyone have any formulas for calculating an estimate on the bandwidth needed to run "x" clients? For example, let's say I'm reselling Cobalt RAQ's and providing 100GB's (random number) monthly transfer for 20 (another random number) clients, how much bandwidth will I need? A 7 mbit connection would allow a theoretical 2,310GB (100GB x 20cust. = 2000GB) of monthly transfer but obviously clients aren't going to have a balanced rate of transfer. I would expect peak usage to be quite a bit higher with low transfer speeds at night.

Basically I'm looking for a formula to calculate:

If I give "x" customers "y" amount of transfer a month I'll need a "z" mbit connection to have plenty of bandwidth for my customers.

Thanks.

Assume you're looking for z, the connection in mbps.

To simplify the model.

b/w by customer = y GB/mth
no of customers = x people
max. cpu 'acceptable average load' = L%

B/w needed = xy (1024)^3 * 8 * (100/L) bits/mth
= 8(1024)^3 xy * (100/L) / (3600 * 24 * 30) bits/sec
= 0.3314 (xy/L) mbps
Connection,z --> (1/3) (xy/L) mbps (rounded)

So, if you have x=20 customers, average b/w by one customer = 30GB/mth, average cpu load = 40%,
thus, needed connection z = (20*30 / 3*40) = 5 mbps

Of course there are many issues to consider, but this serves as a quick method for oversimplified model. :D

Bingo! Thanks that's exactly what I was looking for.

I'm not quite sure I understand how CPU load fits in though.

I think a safe way to do it is to assume you will you an average of 25% the capacity of your line.

2000GB=2048000MB=16384000mb/month
60secondsx60minutesx24 hoursx30 days=2592000 seconds in a month

168384000/2592000=6.32mbps
assume 25% capacity so multiply by 4
that comes out to about 25mbps. Now, you can also assume that very few people will actually use the given amount of bandwidth (unless this isn't the smallest package you are offering in which the percent using near the limit grows exponentially)
5mbps would give you about 400GB of usable bandwidth.

ooppss... typo, was kept thinking about cpu load, sorry. Plz replace the 'cpu' with 'line'.

:D

Originally posted by jw
<snip>
5mbps would give you about 400GB of usable bandwidth.

Thanks for the info.

My next question, how the heck can rackshack afford to provide the bandwidth they do? I understand they have volume but geez.

$.25/gb * 100GB = $25 + rack space + servers + employees for $100/month? How?

Considering they would most likely be buying thier line at a dedicated rate rather than GB's transfered, by your calculations a 10mbit line would host around 800GB's a month or 8 clients.

I just don't understand it. I don't understand how anyone can even compete.

First, everybody loves more resource guarantee, though not everyone will be utilizing all resource offered. It makes us feel secure if more resource is promised. Chances are, before you can consume 300GB/mth, you've already got the 2nd or 3rd server.

Second, rackshack has their own data center. It's not 10mbps or even something close, they are having multiple OC3 lines. Look at their network usage at http://rackshack.net/aboutus/networks.asp .

Third, talking about competition, this is perhaps the most difficult thing to deal with. One needs lots of modal (money) to offer 'something which others can't offer', and a good biz plan too. Also always alert of what were done by competitors (marketing survey), what wanted by clients... etc.

That said, if everything properly planned, it's not impossible to understand why rackshack can offer such a 'great deal'. That's why a successful biz doesn't solely count on technical knowledge but also takes lots of business knowledge/planning.

I understand all your points. I'm just not happy about them :-) I've been doing some market research because I think it's a market segment I'd be interested in getting into. Unfortunately I just can't come up with the capital to be even close to competing with them.

Thanks for all the help