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When are multiple gigabit ethernet ports in a server justifyable?

Posted on 2004-08-18
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Our LAN consists of about 75 PC's, most are P3's and P4's, all are connected to the LAN at 100MB or better, some newer ones have gigabit ports in them, but all are plugged into 10/100 ethernet ports.  Our wiring is CAT5, but most of it is strung casually though the crawl space - not to the ANSI spec at all.  Most of the user's wires are about 50-150 in length.

The backbone consists of 24-port 10/100 switches, a few HPs and a few Dells.  At the top we have a 24-port HP gigabit switch, the 10/100 switches are plugged into this, some using gigabit transceivers and some at 100MB, as well as the servers and top level routers.  Most of the newer servers have multiple GB ports.  Counting PC's, printers, routers, etc.. I'd say we're using 100-110 ports.  Our dozen or so servers are NT4 moving to 2003, and each runs a particular app - RightFAX, security cameras, Exchange, voice mail, file server, PDC, BDC, and the rest are our new servers that will replace some of the older ones.  We are also adding a document imaging SQL server, but access to look up stored documents will be light.

My question concerns the need for multiple gigabit ports on the servers.  My techs feel that we need 2-4 GB ports on each server, connected to a gigabit backbone.  If we were moving many 100MB+ files around constantly, I'd agree we need this much bandwidth.  But, we're not, and the most intensive users are CAD users working on AutoCAD files that average 200-300K, with no files over 5MB in size.  Probably 90% of the users do office work, MS Exchange access with Outlook, Excel, Word, and run a thin client app that talks to an HP Unix/Oracle database.  In my opinion, we have relatively light network traffic for our size.

Does anyone see a need for four gigabit ports in a Windows 2003 server domain controller?  It won't be doing any file sharing operations, just domain "stuff" like DHCP, Active Directory, and DNS.  The file server runs the printers, maybe 10 laserjets in the building.  I can see maybe two teamed GB ports per server on Exchange and the file server, but not on a domain controller or a lightly used RightFAX or voicemail server.

My techs are wanting to put 3-4 GB NICs (teamed) in each server and I'm having a hard time justifying this due to the bandwidth I feel we're using.  It doesn't take long to fill up a 24-port GB switch when you use 2-4 ports per server, and have a dozen servers.  An HP 2825 is about $1,700.  A suggestion has been made that we look into setting up V-LANs before we invest in more GB ports.  Comments?

Thanks!
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Question by:TinsleyC
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mikebernhardt earned 300 total points
ID: 11836310
I completely agree with you. Computer techs always think that they need to add infinite bandwidth to their servers, with no justification for it. 2 ports, just for redundancy, is way more than enough for what you've described.

Aside from your known usage, another way to look at it is statistical. You have 75 users with max of 100mb. Based on average bandwidth usage and the utilization of a server, how many users do you need to have before there is even the potential of congestion on 2 or even 1 gig links? My guess it would be several hundred.
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by:Don Johnston
ID: 11836857
I second Mike's thoughts.

Well said, Mike.

-Don
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by:PennGwyn
ID: 11837097
We're serving two major campuses with hundreds of servers and thousands of workstations.  The only place we team any gigabit connections is along the backbone between major switches, where traffic actually justifies it.  None of our servers are using teamed connections.
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by:bfarmer
bfarmer earned 100 total points
ID: 11837209
Ditto all of the above.

We have a data center with a mix of approximately 300 Sun and Wintel servers.  The only boxes with Gig connections are the high-end database servers and they only really justify it when they're being backed up.

We have Solarwinds monitoring the switches for port statistics, which makes it quite simple to hand the server guys a couple of graphs showing they barely justify a shared 10BT hub, let alone a switched Gig port...

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by:public
ID: 11838023
To make an intelligent decision you need to collect some real traffic data.
Most routers and switches let you collect snmp data.
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by:Pentrix2
Pentrix2 earned 100 total points
ID: 11840050
Your switch should do some graphs on utilization and bandwidth.  It should also display which time it was peaked at and when it wasn't using that much.  The router has the same optionis as well.  Gig connections are not justify in your situation and techs always think they need the Best of the Best without any real understanding of a network infrastructure.
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Author Comment

by:TinsleyC
ID: 11841613
First of all, I really appreciate everyone's answers.  But I do need to defend my techs here, they are knowledgeable in what they do, they're just wanting the "best" network, and are trying to look toward future needs.  But that's where we differ slightly, I can't see the immediate need for more GB ports and I'd rather wait a year or so until their price comes down more and the need is there.

I do need to clarify a couple of things.  Some of the teamed NICs now are 100MB, not GB.  But the new servers are gigabit with multiple NICs.  Also, the facility in question (not my facility) does have about 20 CAD stations, and some run Pro-E, and the files are up to 10MB in size but most average 2MB or less.  

I have a lot of respect for a highly utilized, saturated network.  It means you're getting your money's worth!  Not that I like slow, I just like to use what we buy.

Sounds like the thing to do is some port monitoring to see which ones are most utilized.  
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by:mikebernhardt
ID: 11844345
A good tool to experiment with is MRTG. It's free, runs on Perl, and it will give you very nice graphs of utilization. You can have it poll your switch ports for you (supposedly) most heavily utilized servers, and you'll see exactly what is happening.

You can even set the polling interval for 1 minute (default is fine) to be sure you catch those file transfers. I'd say if you're consistently running at 50% bandwidth you should consider upgrading to gig. You wouldn't need it at that point but you would avoid future congestion issues.

On the other hand, you can wait until you actually see congestion. You already have the right NICs. If there's congestion, move them to Gig ports.
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by:Pentrix2
ID: 11844367
Mikebernhardth, he doesn't have the nics yet.  He was asking if it was justify to purchase them for his servers.  Other than that, I agree with Mikebernhardt on this one too, lol.  :)
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by:mikebernhardt
ID: 11844438
Ah yeah, sorry! My, aren't you agreeable today Pentrix2!   :-)

My psychic guess is that you'll see average usage at around 20% with spikes to 50%. If you're doing network backups those will obviously take a much bigger toll when they're happening. But that's off-hours presumably. If I'm right, I don't see a need for gig links.
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by:Pentrix2
ID: 11844472
hehehehe, :)  

You been on the point everytime, can't help agreeing with you.  :)
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by:TinsleyC
ID: 11844525
Actually, the question is to buy additional gigabit ports when I already have 24, and do I need more than 1-2 connections per server to those gigabit ports.  I feel that one port for low-end servers is fine, two for moderate use servers, and maybe three for high end, like Exchange and a file server.  If we do that, we have no need for another 24 port gigabit switch.
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by:mikebernhardt
ID: 11844601
I think you've got your answer then. There seems to be unanimous agreement that what you're proposing is way more than enough.
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