We are planning around 500 people per node.
Ok you claim you're not overselling.
Lets put this in concrete numbers.
Your using the KS-4 plan from Kimsufi in their BHS location. This specific server has the following specs:
4x 3.1GHz (Max of 3.8 GHz)
16 GB RAM
1 TB HDD (only a single hard drive mind you)
100 Mbps unmetered
You stated that you have a maximum of 500 clients per server at the following plan:
1 Core
32 MB RAM
1.5 GB Storage
No port speed information
Now recall your previous statement that 30% of your customers don't even use it at all (assumed by the fact that 30% does not even open the e-mail as stated by you). This leaves about 350 clients who actually open it up and use it.
Now provisioning wise, you obviously provision the proper VMs, so we're going to assume the unused VMs are still taking up "RAM and HDD Space" (because it's provisioned for them, used or not)
32 MB * (1 GB/1024 MB) * 500 Clients = 15.625 GB RAM Provisioned
1.5 GB * 500 Clients = 750 GB Provisioned
1 Core * 500 Clients = 500 Cores (oh wait... shared use!) = 4 Cores clocked at... lets say benefit of the doubt 3.8 GHz
Well... we forgot fair use for the CPU!
4 Cores * (3.8 GHz/1 Core) * (1024 MHz/1 GHz) / 500 Clients = 31.13 MHz per client
So each client theoretically gets 31.13 MHz per core.
But hey, remember only 30% of them actually use it.
4 Cores * (3.8 GHz/1 Core) * (1024 MHz/1 GHz) / 350 Clients = (31.13 MHz per client)/0.7 = 44.5 MHz per Client
Wow that's 13.37 MHz MORE per person!
Now remember, we have 100 Mbps port speed. But again fair use and with that much client density...
100 Mbps * (1024 Kbps/1 Mbps) / 350 Clients = 292.57 Kbps per VM! Or more than twice the speed of dialup! (assuming Dialup speed is around 110 Kbps)
Now remember that one hard drive! Meh, we'll be generous and give you 100 MB/s for your IO Benchmarks (even though Kimsufis themselves are mostly on recycled hard drives).
100 MB/s * (1024 KB/s/1 MB/s) / 350 Clients = 292.57 KB/s IO
But what does that even mean? Well here's a lovely picture of a parrot I found on imgur!
http://imgur.com/gallery/3tsf3eu
The picture itself is 1.32 MB big! That means it'll take 4.62 seconds for it to write and read from the hard drive. But wait, we also want to service it on the internet! That's another 4.62 seconds!
But lets say we're not interested in sending pictures of parrots, and have other needs that needs to be met. Well lets see how long it takes for us to write onto the hard drive space!
1.5 GB would take 1.5 hours to fill at a network port speed (and IO speed) of 292.57 KB/s.
Look, you're not actually overselling on hard drive space, nor RAM (well... you are technically overselling it because the OS itself also needs room), but you are terribly overselling the CPU, the IO, and the network bandwidth.
@
mtwiscool,
you are overselling your services.
Edit: I realized I forgot to convert from bits to bytes. But whatever.