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I have a VirtualBox VM that is located on a network share of my NAS.
When I copy something from the VM's disk onto another of the NAS' network shares (so the data is visible outside the VM), the Windows 7 Task Manager shows only incoming network traffic (yellow graph). It's as if the data was only received but never sent over the network. I verified that the data arrives on the other network share.

As I understand it, the data flow looks like this:

+-NAS--------+      +-Win7 PC (VM Host)-+
| Share1(VM)-|>---->|-+                 |
|            |      | |                 |
| Share2 <---|<----<|-+                 |
+------------+      +-------------------+

If it was like this, I would see incoming and outgoing traffic, right?

What am I not getting here?

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+1 for diagramming data flow. – Wuffers May 20 '10 at 1:27
Point of clarification, are your actual VM files - your VMDK, VMX, etc, all stored on the NAS? And your HOST is running the VM off shared data? – Cylindric May 21 '10 at 17:16
@Cylindric: Yes. – foraidt May 25 '10 at 17:57

If you are logged into the Win7 PC and copy from Share1 to Share2 (and Share2 is also a VM) then that is what I would expect as well.

If Share2 is not a VM, but just a share hosted on Win7, then I see no need for there to be outgoing network traffic (other than administrative with Share1). A situation more like this:

+---------------------Win7 PC (VM Host)---+
| +-NAS--------+   |                      |
| | Share1(VM)-|>--|-->-+                 |
| |            |   |    |                 |
| |            |   |    +-> Share2        |
| +------------+   |                      |
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Perhaps it is like this:

> +-NAS--------+      +-Win7 PC (VM Host)-+
> | Share1(VM)-|>--+->|->                 |
> |            |   |  |                   |
> | Share2 <---|<--+  |                   |
> +------------+      +-------------------+

Where the host is acting like a manager directing two "employees"(ie. share1 and share2) to work with each other and report the results back to him.

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Counterexample: Copy from a network share to another network share, where both shares are on the same server and the copying is initiated by a client. Then you'll see that the data is first sent to the client (incoming) and then sent to the server (outgoing). – foraidt May 25 '10 at 19:16

You are saying you have a physical NAS box presenting a share \NAS\shareOne, and a VM presenting a share \VM\shareTwo, which is also actually on the NAS, and you're using the HOST to copy from \NAS\shareOne to \VM\shareTwo?

In this case, you will see both directions of traffic, as the data is pulled from the NAS->-VM->Host, and then back out Host->NAS. If you're not seeing that, you're you don't have the data going to and from the NAS.

Source and destination are on the NAS, even if the Host thinks it's putting data onto the VM_GUEST. The guest has to copy it to the NAS for storage anyway, and that NIC is on the Host.

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