Fax Server on a KVM Windows-XP VM (fax transmision reliability problems)

[vcp_ai]

I'm trying this solution, because I have actually an ActiveFax Server installation on a windows XP machine, and it has been working for 4 years without a problem (also have a license for it..) So I'm giving it a try under ProxMox ...

I´m using an external RS-232 serial fax-modem, conected to the only tty port of the main board.
I've correctly installed ActiveFax Server on a KVM Win-XP VM, and after adding:

serial: /dev/ttyS0

to /etc/qemu-server/vmid.conf , Windows VM 'sees' COM1: port and ActiveFax Server program recognizes it as a Clas2-Modem at the first attempt.

Problem is that fax transmision reliability is very bad, 100% of the pages have quality problems, about 20% of every page is lost. Fax transmission report gives no error.
Fax reception is perfect, 100% of received pages are correct.

For test scenario I have mi old Pentium II and Proxmox Virtual machine connected to two different telephone lines.

Win-XP Virtual machine goes very fluid (better than the old Pentium II that is actually running Active Fax), and Proxmox server never goes more that 30% of CPU or 40% of memory used.

As far as I know, faxing is a time critical operation, and I'm wondering if proxmox/kvm/qemu has some option to increase priority to ttyserial emulation, or is there any kind of virtio driver to improve tty emulation.

Thanks in advance

Vicente

 

[JustaGuy]

By default Proxmox relies on the kernel's 'fair scheduling' function to distribute energy between VMs.
You'll see a setting under the "Options" tab in a KVM machine's confguration section called "CPU Units".
This adjusts the relative importance of that machine compared to the others running on the node/host/PVEbox.

This post describes adjusting CPU weights.
If there are other VMs running you could try prioritizing the one doing faxes and see if that helps.

 

[vcp_ai]

By default Proxmox relies on the kernel's 'fair scheduling' function to distribute energy between VMs.
You'll see a setting under the "Options" tab in a KVM machine's confguration section called "CPU Units".
This adjusts the relative importance of that machine compared to the others running on the node/host/PVEbox.

This post describes adjusting CPU weights.
If there are other VMs running you could try prioritizing the one doing faxes and see if that helps.

Thanks for your input. Will try this afternoon.
I will use default value (I assume 1000) for all the machines, and will try 30000 for fax machine...

Will inform.
Regards

 

[JustaGuy]

I just gave it a shot and got this in return:

Bascule:~# vzcpucheck
cat: /proc/fairsched: No such file or directory

Maybe it's because of the 2.6.35 branch, I'm not sure.

 

[dietmar]

[/code]Maybe it's because of the 2.6.35 branch, I'm not sure.

Yes. That only works with OpenVZ enabled kernels (up to 2.6.32)

 

[vcp_ai]

I will use default value (I assume 1000) for all the machines, and will try 30000 for fax machine...
Regards

Tested with 30000 for fax VM and same sympthoms:
Receive correct, but transmit fails .....

Vicente

 

[shijobaby]

http://expwinproblems.blogspot.com/2010/11/problem-when-sendreceive-fax-using-fax.html