Writing Output on network is very slow - CPU Usage issue

[boutet_gaetan]

Hello, It seems Vray 6 uses better CPU power than before and that's good news ! But that causes a real problem when saving on the network on a another computer rendering a Vray Scene.

I have two powerful Ryzen computers that render super fast, let's call them computer A and Computer B. I have a 10Gbit ethernet network that writes at 250Mb/sec.
I use 3dsmax Backburner to launch my renders and all the rendered frames are saved on computer A.

When computer A has finished rendering an image it writes the output on his own disk pretty fast, 5 seconds for 5 render elements PNG files. (2500x1000 - total size 25mb)
When computer B has finished rendering an image it writes the output on the network disk of computer A extremely slowly. 45-60 seconds for the 5 render elements PNG files !

The reason is simple: when B writes on the A disk computer A is rendering with Vray at 100% usage at the same time. Writing on his disk is not a priority and B has to wait to write on A's disk.

I am using Vray for more than 10 years now and I never saw my computers strugling that much to write the output on a network computer rendering at the same time.
The only solution I found is to low down the CPU priority to Low or lower than normal in the task manager, but at each new scene it resets.

Any ideas ? No option to lauch backburner renders in lower CPU priority ?

This is slowing down my workflow and it is so frustrating to see a Ryzen 5950x rendering for 60 secs and writing the files for more than 45 sec...

Thanks.
Gaëtan

[Joelaff]

I assume you mean a 10Gbit Ethernet that writes 250 MB/sec (MegaBYTES, not bits), since 250Mb/sec would be horribly slow. Even 250MB/sec is pretty slow on a 10Gig link, likely the drives on the other end? That network should do 800-1000MB/sec or slightly more.

I would try adjusting your Adapter settings for your Ethernet card and in the Configure... button Advanced tab try disabling Interrupt moderation. Oddly this often makes it much faster, which is funny since the idea of this feature is to reduce CPU overhead. It's not needed much with modern CPUs. Also try disabling DMA coalescing (packet coalescing) as well.

If that doesn't fix it you would try reducing the number of threads VRay uses with VRAY_NUM_THREADS .

See here:
https://docs.chaos.com/display/VMAX/...ment+Variables

Also, make sure you are using at least hotfix 2 of VRay 6, as this fixes a serious slowdown to the system interactivity when rendering.

Edit: I think I see your issue, though. You are writing to machine's A drive, not a standalone server. And machine A is rendering. Perhaps try that VRAY_NUM_THREADS on machine A, and set it to 1 less than the number of cores. But I would still check your network (above) settings on BOTH machines as well, as this could be related.

[boutet_gaetan]

Thank you for your complete reply, as you noticed I am not a network expert

I will try for your ethernet settings recomandations.

I found a temporary solution: I launch Backburner Server in Low Cpu priority, all the 3dsmax sessions it will launch will also be in low priority.

[Joelaff]

Good solution!

I would still check and benchmark test the network settings. I think there is likely room for improvement there as well, assuming you are writing to a SSD or M.2 drive. A spinning rust drive probably can’t go any faster.