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Old 06-24-2008, 09:43 AM   #1
Registered: Feb 2003
Location: Orangeville
Distribution: Fedora
Posts: 461

Rep: Reputation: 31
Network slower than expected, how do I detect the cause?

My network topology is structure.

2 WAN NetGear FVS124G   --> Dell PowerConnect 2724         
Wireless DLink DIR-625  -------|
Then all my internal wired equipment is connected to the PowerConnect, wireless goes through the DLink.

When I put this in place I was getting 60MB/s transfers from my laptop to server. (which is the speed of the HDs) Now I get about 15MB/s almost consistently over my entire network.

I tried power cycling the entire array and I'm now getting 38MB/s through iperf still only 15MB/s with scp. With a 1 GigBit Router I would expect it to be much higher since with a 100Mbit line I was getting 9MB/s transfers.

The Xen array I'm getting anywhere from 2-10MB/s, I know I have a problem there with the xen machines talking to each other.

Things that have changed:

I've reformatted the server into a pile of xen machines. All servers I've switched from DHCP (controlled by to Static IP. Upgraded two of my four home computers to Fedora 9 from Fedora 8.

So my questions:

1. on a GigBit network what speeds are other people getting? Was my 60MB/s just a fluke and I'm looking for nothing?

2. Where do I start looking? Currently I'm still rebuilding the DB on my Xen array so I can't shut it off at the moment to see if it's the cause.

Can any one point me to some places to check?
Old 06-25-2008, 02:06 AM   #2
Registered: Jul 2007
Distribution: Red Hat CentOS Ubuntu FreeBSD OpenSuSe
Posts: 252

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Have you checked if there are collisions on your switch? How about the NIC of the servers?
Old 06-25-2008, 03:29 PM   #3
Registered: Feb 2003
Location: Orangeville
Distribution: Fedora
Posts: 461

Original Poster
Rep: Reputation: 31
Originally Posted by tajamari View Post
Have you checked if there are collisions on your switch? How about the NIC of the servers?
Yep. The powerconnect has no collisions or dropped packets. The dhcp/wan router had ~700 Collisions on WAN2 but nothing on the LAN side.

Just for fun I tried something:

Server listening on TCP port 5001
TCP window size: 0.08 MByte (default)
[ 5] local port 5001 connected with port 58961
[ 5] 0.0-30.0 sec 8030 MBytes 268 MBytes/sec

I hit the interface card from itself. I get 268 MBytes/sec. So how did that work. Did that send traffic to the router then back to the card or did that all run within the card itself?


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