Windows 2016 Guest bridged network extreemly slow

[HAKAK]

Hello folks,

I have problems with bridged network speed from my Windows 2016 VMs to other machines in my net.
Situation:
Machine: DELL XEON Silver 8 physical cores NIC BCM57416
Host: debian 10.1 (1 core)
Guests: 1 debian 10.1 working as samba file server Paravirt. Provider: KVM (1 core), 2 Windows Server 2016 Paravirt. Provider: HyperV (3 cores each)

My problem is that the Windows machines show an extreemly poor network speed, whereas the debian is ok.
A backup of about 200 GB of data of the Windows VMs lasts over 24 hours regardless to what share (samba or NAS attached to the net).
I tried several virtual adapters for those machines with no better results either.
Although the physical NIC on the host is working at "only" 1000 GBit/s due to autosensing, network speed of the Windows VMs makes working with them almost impossible.
What can I do?

[scottgus1]

Please pick one guest that is demonstrating this problem. Shut the guest down completely from within the guest OS so the Virtualbox guest window is gone and the guest is shut down not save-stated. Then boot the guest again, run until you see the problem, then shut down the guest again from within the guest OS. Zip and post that guest's Vbox.log and the guest's .vbox file, using the forum's Upload Attachment tab.

Is the backup you are copying one large file or several small files? How are you copying the file(s)? Some years ago I ran into abysmal network speeds copying large files on a Windows 7 PC, until I tracked down that there was some problem with buffering large files in Windows when copying via Explorer, and the 'xcopy /j' command and switch cleared up the problem, by turning off buffering for that command run.

Do you have the same slow speed copying the backup to another physical disk (not the disk the guest is stored on) on the host PC via a shared folder on the host?

[HAKAK]

Thanks for your reply.

Please pick one guest that is demonstrating this problem. Shut the guest down completely from within the guest OS so the Virtualbox guest window is gone and the guest is shut down not save-stated. Then boot the guest again, run until you see the problem, then shut down the guest again from within the guest OS. Zip and post that guest's Vbox.log and the guest's .vbox file, using the forum's Upload Attachment tab.

Can do this only on Sundays when I can shutdown the VMs.

Is the backup you are copying one large file or several small files? How are you copying the file(s)? Some years ago I ran into abysmal network speeds copying large files on a Windows 7 PC, until I tracked down that there was some problem with buffering large files in Windows when copying via Explorer, and the 'xcopy /j' command and switch cleared up the problem, by turning off buffering for that command run.

The backup is made by Cobian-Backup an consists of several thousands of files.

Do you have the same slow speed copying the backup to another physical disk (not the disk the guest is stored on) on the host PC via a shared folder on the host?

Have tried it. Also the same, i.e. pretty slow (estimated by Windows >5 h for about 40 GB).
I think the problem is caused by poor I/O of the attached virtual disk. On Sunday I'll change the virtual adapter of the disks and will post again the results.

Thanks

[scottgus1]

I think the problem is caused by poor I/O of the attached virtual disk. On Sunday I'll change the virtual adapter of the disks

If you mean that you'll try IDE vs SATA vs something else, I doubt that will change much. Maybe a bit more overhead for IDE because it's older, but I doubt it. Back long ago there was a flurry of activity over whether XP, originally an IDE OS, would benefit in Virtualbox from being switched after install to SATA. I don't recall any blinding speed increases.

[socratis]

I don't recall any blinding speed increases.

Because there weren't any...

[HAKAK]

scottgus1 wrote:
If you mean that you'll try IDE vs SATA vs something else, I doubt that will change much. Maybe a bit more overhead for IDE because it's older, but I doubt it. Back long ago there was a flurry of activity over whether XP, originally an IDE OS, would benefit in Virtualbox from being switched after install to SATA. I don't recall any blinding speed increases.

You are right. The speed increased only from the above mentioned >5h to about 3 and a half h, after changing adapter to SATA.

Attached you'll find the two files copied in situation you described.

Thanks

[HAKAK]

No solution in sight?
Thinking, my combination with a debian host and several Windows 2016 Servers on a Dell Machine with a BCM57416 NIC should not be too exotic, I wonder why network speed on this system shoudn't be better.
The yesterday backup ran with an average speed of 7.11 Mbyte/s. Not very satisfying .
The only thing I found is a VMQ issue with Broadcom controllers and Hyper-V. However, I couldn't find out how to switch off this feature in a debian host.

[Martin]

Can you test a

Code: Select all

ping /f /l 1500 <IP address>

to your NAS or file server from the Windows 2016 guest?

[HAKAK]

ping /f /l <IP-address>

• Paket müsste fragmentiert werden, DF-Flag ist jedoch gesetzt.

Edit: I have controlled all NICs involved. MTU is set to 1500 on every NIC.

[Martin]

Looks like the path MTU discovery is not detecting the network limits correctly.
Could you try lowering the MTU in the Windows guest?
I have seen very similar file transfer slowdowns with fragmented packets.

[HAKAK]

Thanks for trying to help.
It was not an MTU issue.
The network is a peer-to-peer-network.
Since not having installed those Windows-Boxes myself, and my Windows coworker is in holidays I logged in one of these Windows machines.
I tried an nslookup on the short names in the domain and nothing worked. FQDNs are resolved properly. I entered the domain suffix in the configuration of the network interface.
Now I have the desired speed with these machines.
Thanks again to everyone who tried to help.