Very slow network file transfers

networking

For some reason, our network is very very slow when it comes to transferring files internally thru LAN (gig).

Some numbers:

C:\iperf-2.0.5-3-win32>iperf.exe -c 192.168.100.12 -w 256k
------------------------------------------------------------
Client connecting to 192.168.100.12, TCP port 5001
TCP window size:  256 KByte
------------------------------------------------------------
[  3] local 192.168.100.73 port 36705 connected with 192.168.100.12 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   385 MBytes   323 Mbits/sec

That's from a physical Windows 7 to a virtual Windows Server 2012R2.

Reverse (from the same virtual Windows Server 2012 R2 to the same physical Windows 7) isn't much better, if at all:

C:\Users\U1\Desktop\iperf-2.0.5-3-win32>iperf.exe -c 192.168.100.73 -w 256k

------------------------------------------------------------
Client connecting to 192.168.100.73, TCP port 5001
TCP window size:  256 KByte
------------------------------------------------------------
[  3] local 192.168.100.12 port 25464 connected with 192.168.100.73 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   431 MBytes   361 Mbits/sec

Another test:

C:\Users\U1>robocopy \\cd2012\d$ c:\temp dummy*.txt

-------------------------------------------------------------------------------
   ROBOCOPY     ::     Herramienta para copia eficaz de archivos

-------------------------------------------------------------------------------

  Inicio: Wed Apr 08 20:58:57 2015

   Origen : \\cd2012\d$\
     Destino : c:\temp\

    Archivos: dummy*.txt

  Opciones: /COPY:DAT /R:1000000 /W:30

------------------------------------------------------------------------------

                           1    \\cd2012\d$\
100%        Nuevo arch                   537.0 m        dummy.txt

------------------------------------------------------------------------------

               Total   Copiado   OmitidoNo coincidencia     ERROR    Extras
Directorios:         1         0         1         0         0         0
 Archivos:         1         1         0         0         0         0
    Bytes:  537.00 m  537.00 m         0         0         0         0
    Veces:   0:00:16   0:00:16                       0:00:00   0:00:00


Velocidad:            33409594 Bytes/s
Velocidad:            1911.712 Megabytes/min

Finalizado: Wed Apr 08 20:59:14 2015

Shows similar results.

I did this when no PCs were on and noone else was in the office using bandwidth. At best, WSUS. Tried it this morning as well and basically same thing happened.

The issue is that but the bigger issue here is how exactly to go on troubleshooting.

Wireshark comes to mind but personally I admit, I do not have enough technical knowledge to view Wireshark and see exactly what is happening. I would need some kind of guidelines and filter tips to know what to put in filter and what to look at exactly so I can watch out for certain flags and know where it is coming from.

Ive also thought about limiting all connections except from my PC and see if it is a PC with some kind of spyware sucking up all the internal bandwidth.

I've checked for rouge DHCP servers and as far as I see, there are none on the network.

The logical choice would be to unplug EVERYTHING from the network and work my way plugging back in but for a business the downtime is very costly so that's why slowing the network down came as a idea.

Any tips on what to do and what not to do?

Best Answer

Network performance problems rarely are a simple thing to diagnose, especially when virtual hardware is thrown in the mix. Let's try to isolate the weak spot...

1) use iperf to measure a PC to PC connection: in this manner, you will exclude any virtualizer-related problem. If the results are satisfactory, proceed with step 2. If not, repeat that same test with another 2 PCs with different networking hardware. If the bandwidth is OK, then you have a problem with your first PC. If not, you probably have a switching problem.

2) use iperf to measure a PC to virtualizer connection: now let's examine the connection between your PC and the physical virtualizer server. If the results are OK, then network connection between your PC and the server itself is not the problem. Proceed with step 3.

3) if the PC-to-Server connection is OK but PC-to-VM is slow, probably the culprit is the virtual adapter. If you can, use a paravirtualized network adapter/driver for your virtual W2012 installation. The difference can really be big

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