the latest sp indicates the following:
When writing a raw .exr file, V-Ray will attempt to produce a scanline version of the file instead of tiled one
in what cases will vray fail at saving a scanline exr and are there any downsides to trying to get vray to save a scanline exr in terms of ram usage?
V Miller
It will fail if you turn off the “use memory frame buffer” option for sure. Otherwise, at the end of the rendering, V-Ray will take the memory buffer, write out a second scanline .exr file, delete the original tiled file, and then rename the scanline file to the original name. To be honest I have not measured how much memory the scanline conversion takes beyond the obvious amount needed for the memory frame buffer.
Best regards,
Vlado
Vlado just as an aside would it be possible to get a few options added in to this similar to the flags in the vrimg2exr command line? As a preference I’d always like ZipS compression and the datawindow turned on for nuke as they make another huge difference to the redraw speed of files - would it be a big deal to add in compression, color depth and datawindow options into the save dialog?
good to know since as a rule I usually leave the memory frame buffer off as I always believed it sucked up resources. I think the additional options that joconnell mentioned would be a great addition.
V Miller
It’s not that difficult. Will make a note for it. BTW there is already an option for the color depth.
Best regards,
Vlado
It does 
However for the scanline .exr we really need the frame buffer to be in memory.
Best regards,
Vlado