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BBonifield
Contributor
Contributor
‎01-26-2011 07:59 AM

Limited throughput when accessing host network or outside world

I have a new VMWare ESXi install with two CentOS VMs.  VMWare tools are installed on both VMs, and I don't get any packet loss when I ping either of the guest VMs from a stand-alone machine on the network.  However, the throughput from the guests to the rest of the true network or the outside world is extremely limited.  At some points, it'll drop as low as 10K/s.  I can transfer files between the two guest VMs at high speeds (~5MB/s).  Also, I plugged a laptop into the same switch port with the same network configuration, and it didn't have throughput issues.  Suggestions?  I'm at a loss here.

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BBonifield
Contributor
Contributor
‎01-26-2011 08:08 AM

I should also note that this only applies to DOWNSTREAM throughput.  I can upload files to external hosts very fast.

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J1mbo
Virtuoso
Virtuoso
‎01-26-2011 08:47 AM

What switch is the host connected to?  How many vSwitches are defined and how many physical NICs are on each?  What is the spec of the host?

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BBonifield
Contributor
Contributor
‎01-26-2011 08:53 AM

The host is a Dell PowerEdge T100 (dual-core 2.4ghz, 2GB ram, 1 NIC), and it is connected to a Dell PowerConnect 2724.  1 VMSwitch connected to the lone host NIC, and each guest VM has 2 virtual NICs.

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J1mbo
Virtuoso
Virtuoso
‎01-26-2011 09:01 AM

OK, what vCPU and RAM is allocated to each VM, what disk(s) are in the server and how are the two vNICs configured in the guests?

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RyanSpence20111
Contributor
Contributor
‎01-26-2011 09:36 AM

I had the same issue a few days ago and I can tell you exactly what was wrong. Check your NIC speed in in vSphere and make sure it is set to exactly what your port speed is on your switch. My NIC was set to 100 Full, while my switch was on 100 Half, I was getting .5Mbps down and 1.9Mbps up, I change the switch to 100 Full and now I get 75Mbps down and 60Mbps up.

Please remember to award points if you found this post helpful.

Ryan Spence

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BBonifield
Contributor
Contributor
‎01-26-2011 09:38 AM

The host itself has two 250GB SATA 7200 drives, combined together into a single data store on the host.  Each VM has 1 vCPU and 256MB RAM per VM, and the two VM NICs are configured to use static IPs, although i have tried it with DHCP as well.

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RyanSpence20111
Contributor
Contributor
‎01-26-2011 09:41 AM

Set your switch port speed to match exactly what is configured on the physical switch. That is your problem, same issue - transfer between hosts was fast- outside world speed was slow = switch is not set to the speed your host is.

Please remember to award points if you found this post helpful.

Ryan Spence

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BBonifield
Contributor
Contributor
‎01-26-2011 09:49 AM

Wow...  I can't believe it, but you're right.  Switching from full-duplex to half-duplex fixed the problem.  I didn't setup the network here, but I would have bet money that the network was full-duplex.  In any event, thanks a bunch!

Uhh, what the heck?  I can't award points after I mark it answered?

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RyanSpence20111
Contributor
Contributor
‎01-26-2011 10:06 AM

I'm glad I could help! It's amazing how simple a fix can be Smiley Happy

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