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  1. #1
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    100mbit Connection Saturation - # of Servers

    Ok, I know that there really isn't a definitive answer to this question. Obviously it is an educated guess. But, we are looking in to some colo options for our servers and a client that will share a rack with us.

    Looking at the pricing and options we will most likely end up with a 36" bakers rack and a 100mbit port. There will be around 10 servers to begin with on the rack, most of which will be webservers that are not really at capacity.

    My question is this, my client is worried about sharing a 100mbit line b/c he feel it will get saturated with his 3 servers, one being a db server that he says will have 100,000 users logged on and requesting once every 15-30 min. And two webservers that might transfer a TB/month with some heavy bursting. Is it possible for these servers to saturate a 100mbit line? I mean, getting a gigabit drop is just stupid by all standards, IMHO. And, I know the client isn't going to pay for that. Basically I need your opinion on the saturation and what do people generally do in this case? All systems would obviously have a 100mbit NIC. Do most DCs offer two drops?

    Also, when companies like rackspace and other lease based dedi resellers offer 100mbit connections on their servers, they are talking about a 100mbit NIC on a gigabit connection droped into a cage which is shared with 100 servers or so, correct? So, those systems get saturated as well? He seems to think he would be better off with one of these resellers b/c he is getting a 100mbit connection on his server.

    Thanks for your input.
    Last edited by Ackoo-jt; 10-18-2005 at 12:24 AM.
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  2. #2
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    The 3 servers your client has will probably not saturate a FE drop. On average, a TB/month only works out to 3mbps. In theory, a 100mbit drop can push 30TB of traffic if it is saturated 24/7 in a month.

    If you are trying to keep things fair, you can try to set the port on your switch as 10Mbps Full duplex or try to create QoS on your switch to make sure every server will have the bandwidth it needed to a reasonable degree when it is needed.

    For company like rackspace, I would guess they will have subnets of dedicated feed into a distribution switch where it uplinks a gigabit to the core. The uplink would be saturated if every system pushes the full 100mbit at the same time. But in reality, that would rarely happens and a provider usually can make a reasonable guess as where that whole subnet would busrt to on average.

  3. #3
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    Originally posted by Mfjp
    On average, a TB/month only works out to 3mbps.
    Bull.

    In theory, a 100mbit drop can push 30TB of traffic if it is saturated 24/7 in a month.
    So which is it, "on average", or "in theory"?



    Brandon

  4. #4
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    Originally posted by Mfjp
    On average, a TB/month only works out to 3mbps. In theory, a 100mbit drop can push 30TB of traffic if it is saturated 24/7 in a month.
    Based on common usage patterns for web traffic, I'd say 15-20TB is much more realistic.
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  5. #5
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    ok, thanks, but that still gets me back to saturating that 100mbit line. It that really that possible with 3 servers?
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  6. #6
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    You can saturate a 1,000 mbps GigE with 3 servers
    It is certainly possible to saturate a 100 mbps line with one server.

    Ask to look at thier existing traffic patterns

  7. #7
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    Re: 100mbit Connection Saturation - # of Servers

    Originally posted by Ackoo
    Also, when companies like rackspace and other lease based dedi resellers offer 100mbit connections on their servers, they are talking about a 100mbit NIC on a gigabit connection droped into a cage which is shared with 100 servers or so, correct? So, those systems get saturated as well? He seems to think he would be better off with one of these resellers b/c he is getting a 100mbit connection on his server.
    It sounds like you're asking if you should reasonably expect 100Mbps throughput from a 100Mbps port. If you're paying for the bandwidth, the answer is yes. Companies "like rackspace" are typically smart enough to increase the size of their access switch uplinks or shuffle customers onto different switches so they have plenty of capacity available to sell.

    Keep in mind that some providers make margin on the bandwidth they sell, while others are selling at a loss and betting that most customers won't use most of the bandwidth they are paying for. "Unmetered" servers / co-location may be something you want to stay away from. That said, there are certainly providers offering congestion-free unmetered service, but you are more likely to encounter congestion when buying that type of product.
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  8. #8
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    Ok I am confused.

    Isn't it 3 servers comprised of 1DB and 2 webservers? Do the users get to the DB only via one of the webservers? If so then the bottleneck is the switch and traffic between DB to Webservers never traverse the 100mbit uplink.

    So for the purposes of sizing this we are really only looking for http/https traffic from clients to the webservers across the uplink.

    I am just assuming they are not remotely connecting directly to the DB if they are then just ignore everything I just said
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  9. #9
    One TB a month is only about 3Mbps, as mfjp said above.

    Not sure where cbtrussell is getting his numbers, but its basic math.

    Here's a handy-dandy bandwidth calculator.
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  10. #10
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    Quote Originally Posted by Ripside
    One TB a month is only about 3Mbps, as mfjp said above.

    Not sure where cbtrussell is getting his numbers, but its basic math.
    Sorry, you are wrong. Asked and answered countless times before.

    But I'll tell you what. Put the hardware of your choice on a 10 meg port and let 'er rip. Post the link to your port utilization graphs and let us all watch it for a month. If you hit the magical 324GB for each 1mbps of 95th percentile utilization, I'll post a public apology along with a picture of me holding a sign that reads "Ripside is my hero".

    If you lose, you do the same but your sign reads "Basic math is for kiddie hosts".

    Here's a handy-dandy bandwidth calculator.
    Sorry to have to be the one to tell you this, but just because someone puts up a page using the same incorrect assumptions you've made does not make you both right.

    In all seriousness, please take the time to thoroughly read the content on the page below. It will help you understand why you shouldn't continue to insist that everyone should expect to get 324GB of transfer for every 1mbps of 95th percentile utilization.

    http://inconcepts.biz/cr/95th.html

    Take care,

    Brandon
    Last edited by cbtrussell; 10-31-2005 at 03:23 PM.

  11. #11
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    crnc.net Bandwidth Converter: Mbps to GB Transferred:
    http://crnc.net/network/bandwidthconversion/
    3mbps-972gb
    Strictly about 1TB
    Sorry cbtrussell your wrong again.
    Have a nice day =)
    Last edited by wifiguru; 10-31-2005 at 03:39 PM. Reason: Letter

  12. #12
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    Quote Originally Posted by wifiguru
    crnc.net Bandwidth Converter: Mbps to GB Transferred:
    http://crnc.net/network/bandwidthconversion/
    3mbps-972gb
    Strictly about 1TB
    Sorry cbtrussell your wrong again.
    Have a nice day =)
    Actually, you're an ignorant fool. Take the time to read his post, and read the link and educate yourself.
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  13. #13
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    Hehe, i just got told.
    I was just having fun, peaople need to chill sometimes.

  14. #14
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    If you want to have fun, go to the playground. If you want to learn something useful, and stop being an ignorant noob, read what people have posted before telling someone they are 'wrong again'.
    Jay Sudowski // Handy Networks LLC // Co-Founder & CTO
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  15. #15
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    The saturation point is not going to be 3 servers using 1TB each.
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  16. #16
    Sheesh, feel pretty strongly about this, guys, dontcha?

    I wasn't talking about 95th percentile, OR a 10Mbps connection. He asked about 1TB. I simply gave the strict conversion numbers. Of course in reality its less than that because of overhead with every IP packet, which can vary with different MTU's, keep-alives, file sizes, etc.
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  17. #17
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    There is no definitive answer to your question, only way you will know is to try it.

    What I will say though, I personally had an FE drop on which the bandwidth graphs were showing probably no higher than 80mbps usage at peak times across the switch (2 min avg's). Switch load was pretty low.

    However when I upgraded the line to a GigE, the performance difference was huge ... something somewhere was clearly hitting the top, without any obvious signs.

    As others have said, also read the link to Jeff's website - very good explanation on 95th percentile billing, something you'll find useful when doing your calculations.
    Last edited by dkitchen; 10-31-2005 at 08:27 PM.

  18. #18
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    Basically, you'll find you can shift a maximum of 200GB/Mbps unless you have some strange and really predictable bandwidth usage times using 95th percentile.

    However, I believe the problem here is that your client may be transferring 100Mbps instantaneously, not for the entire month, and that you need to provide some sort of QoS guarantee?
    Of course it's possible for two frontend and one backend servers to max out 100Mbps, however it's probably not as likely as he thinks it is.
    It's best to talk to your provider and ask what they'd charge on top of the current quote for the capability to burst to 1Gbps. The other way of qualming their fears would be to provide QoS at your switch, but that's by no means a perfect solution.
    For now, I would see if the provider would upgrade you to 1Gbps burst for a reasonable amount, and if they would, go with them and monitor RTG closely.

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