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We are experiencing file transfer issues. I try to troubleshoot this problem but it is really hard.

Here is a screenshot I took while transferring a file from my workstation to another server. The screenshot was taken from the workstation (source):

  • The whole graphic was taken during the file transfer, there was no pause on the transfer or anything.

enter image description here

It doesnt stop to flicker like this. And the ETA of the transfer always changes from 10 minutes to an hour or so, and then gets back to 9 minutes, then back to 100 minutes, so on so forth.

Here is the iperf result:

enter image description here

How can I troubleshoot this issue?

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  • Possible network storm? Are your switches managed?
    – Tim
    Dec 6, 2011 at 19:53
  • It isn't clear to me, is that graph from the server?
    – Zoredache
    Dec 6, 2011 at 19:59
  • How big is the file? Does it ever transfer successfully? If so how long does it take? The workstation and server are connected how?
    – dbasnett
    Dec 6, 2011 at 20:51
  • There is only a single Dell PowerConnect 5324 (with the latest firmware version) between the two hosts. How can I diagnose if the switch is faulty?
    – Jonathan Rioux
    Dec 7, 2011 at 13:28

2 Answers 2

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Try wireshark on the server and/or the client. I would guess there is a network congestion going on that forces down the sliding window TCP size of your transfers. Are all components connected with rx/tx flow control set to "on"?

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  • How can I detect if my TCP size has been reduced due to network congestion?
    – Jonathan Rioux
    Dec 7, 2011 at 13:26
  • If rx/tx flow control is on the corresponding counters should grow (on the switch/router and/or server side). There should also be a sliding window negotiation visible. See the WiKi for details
    – Nils
    Dec 8, 2011 at 22:00
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It seems less likely to me that your problem would be a networking issue. I would consider an I/O bottleneck first. Check your server's disk idle time during the transfer and try to find possible interconnections with the drops in your transfer rate.

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  • I think iperf.exe does not write anything on disks, it just tests the network bandwidth between two hosts, am I right?
    – Jonathan Rioux
    Dec 7, 2011 at 13:24

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