Networking too slow

[Campus]

Hi,

I am trying to setup a VBox VM running Win7 Ultimate which hosts the DVBViewer Recording Service which connects to a SAT>IP server to create TV recordings. This VBox installation runs on a ReadyNAS 516 NAS box with an Intel Core i3-3220 @ 3.30GHz and 16GB RAM. The VM has 4 CPUs and 4GB RAM assigned. The recordings are written to a samba share on the same NAS.
Problem is: When doing multiple recordings at the same time the recording service is no longer reachable because the network within the VM no longer accepts connections. At the same time I can still connect to the VBox RDP session without a problem. The VM is configured with bridged networking and I tried both the E1000 and virtio network device but it made not a big difference. The data rate is between 250kB/s and 1.5MB/s for a single TV channel. The problem already starts when trying to make three recordings at the same time. So the combined required network throughput in that case would (worst case): 3x1.5MB/s for reading the stream from the SAT>IP-LNB and 3x1.5MB/s to write the stream to the samba share = 6x1.5 = 9MB/s which should be no problem at all. The entire physical network is using 1GB connections.

I tried strace to see the system calls of the VBox process and it's pretty much all the time doing select() calls.

What can I change to have this VM get acceptable performance? I tried the exact same installation on a real machine running a Intel Core i3 M 370 @ 2.40GHz and there I can make up to 8 parallel recordings writing to the exact same NAS without any problem although the CPU is much slower.

Thanks a lot,
Campus

[Martin]

Well, you have a dual core CPU with Hyperthreading and a VM with 4 vCPU.
There is nothing left for the host, and the Hyperthreading cores are really of no use for virtualization.
Try setting the VM to just one core, so that the host still has a core left to move the date and control the VM.

[Campus]

Hi Martin,

thanks for your reply. The host system is not slow when the problem comes up. I tried to explain this by writing, that I am still able to connect to the guest using the VBox RDP-port (the usual 3379). When the guest is so slow in networking, the host still idles with 70%. Also the samba process on the host machine shows almost no CPU load.
I tried to run the VM with all CPU configs possible (1 up to 4) but it makes not really a difference. To me it looks like VBox networking is saturated with 20 active network connections and this small throughput.

Best regards,
Campus