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If I know how many users will be using a site, and about how many will be on at once, and I can approximate how much data is being transferred between the user and server, how can I calculate the amount of bandwidth the server needs?

735Tesla
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    That's a fairly high number of assumptions, if you don't have existing data for these numbers. – mfinni Jan 09 '14 at 17:11
  • What kind of data is being served? How is it being served? – 89c3b1b8-b1ae-11e6-b842-48d705 Jan 09 '14 at 19:09
  • that's usually not the way to go before contracting network bandwidth, the right way should be by simulating load and concurrent users to determine max concurrent users and the needed bandwidth, then you should account for spikes of concurrent users and load if you have relevant content. – Marcel Jan 09 '14 at 21:11
  • Why not show what you've tried or researched so far? – Drew Khoury Jan 09 '14 at 22:14

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Data per user per second * # of concurrent users - this should be pretty obvious, are you really asking something else?

MDMarra
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  • No I was just curious if there were any other factors that I was not considering. Are there? – 735Tesla Jan 09 '14 at 17:05
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    Well, assuming you're using Ethernet and IP (I'm sure you are) there's approximately a 20% protocol overhead, so a 1Gbps link can handle 125MB/s in theory, but in practice you'll be able to put ~100MB/s over it. Other than that, it's straight multiplication. – MDMarra Jan 09 '14 at 17:06
  • Well, not entirely true. Some webservers and OS would handle just as much open connections as your tuning-fu goes. You can have all bandwidth available and still not being able to serve a high number of concurrent users. Straight multiplication will only serve as a basis for a very low amount of concurrent users. – Marcel Jan 09 '14 at 17:35
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    @Marcel The OP asked strictly about bandwidth calculations, not anything else. – MDMarra Jan 09 '14 at 17:36
  • @MDMarra you're right but then you'll be stalking OP looking for 'i cannot reach max number of users' question just to answer it and win some more reputation points and some copper coins... – Marcel Jan 09 '14 at 20:42
  • @Marcel sorry that you feel like I didn't answer the question, but 5 other people PLUS the OP did, so I'm not sure what you're bent out of shape about. If you'd like to discuss this more, I'm in [chat] fairly frequently. Drop in. If you feel like you have a **better answer** then post it instead of being snarky in the comments. – MDMarra Jan 09 '14 at 20:43
  • My first comment was only to point out that plain 'X times Y' hardly solves capacity planning estimation. – Marcel Jan 09 '14 at 20:47
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    The OP didn't ask for capacity planning for *all facets* of a web server. They asked "knowing a single user's bandwidth needs and how many concurrent users I will have, how can I calculate how much bandwidth I will need?" I think you're wishing that this was a question that it is not. But again, if you'd like to discuss, come in [chat] as opposed to muddying up the comments. – MDMarra Jan 09 '14 at 20:48