Deciding what card to buy for a specific camera in order to get the fastest performance of which the camera is capable without spending more than necessary on a card that is even faster than the camera is capable of taking advantage is a daunting task. Not only can it be very confusing when comparing speeds of various cards, but learning how fast a write ...
I have a K-3 with both the "FLUCARD PRO 16 GB O-FC1" and a "SanDisk Extreme" Class 10 80MB/s 32 GB.
The SanDisk stores images about twice as fast as my FluCard.
I've figured this with the following test:
Erase the memory cards.
Set the K-3 to manual exposure, 1/500th, Motor Drive H (9 shots/s).
Hold down the shutter for as long as the camera takes ...
It seems extremely unlikely that Lightroom would include a setting (whether obvious or secret) to deal with this obscure situation.
I think you're in a situation where the old joke applies:
Doctor! It hurts when I do this!
Well, don't do that.
You have a workaround. I'd focus on making that as painless as possible.
This is normal and expected. It's basically queuing theory. Here's an analogy that might help in visualizing this:
If you walk into an empty store (sensor/camera), grab an item (light/data), and get in line (buffer) for the cash register, they'll ring you up right away (write to SD card), and you're on your way.
If you walk into a packed supermarket and ...
Look at your CPU and RAM usage during a simple export (not a bunch of processor-heavy stuff like noise reduction, moire, clarity). If either CPU or RAM are maxed out they're your bottleneck. Given that 90ish% (or # of cores x 90% for a Mac) is effectively maxed out.
Only if both are some distance from maximum should you consider drive speed as a bottleneck.
There are two things going on when you're shooting a video. Capturing/Processing and writing to the card.
Capturing/Processing -- You don't have to worry about this part. A manufacturer of any camera will guarantee that it will be sufficient. So it is a given.
Writing -- This is when the data is actually written to the card, and of course not cards are ...
Most cameras have an internal buffer they write the pictures to first. From there, the images are written out to the (much slower) memory card. So, if you take pictures at maximum speed, your buffer will be full after some time (My Canon EOS 60D can make about 50 JPEGs or 12 RAW images until the buffer is full).
After that, I have to wait until at least ...