If you are a pro, do you use two card slots for backup? Locked

Noogy wrote:

LensSodomist wrote:

The primary reason for the 2nd slot is to mirror the files from the first card.

Redundancy is what the 2nd slot is all about.

Of course you could also use the 2nd slot as an overflow drive, or place just JPGs there, but to my thinking (coming from an IT background) the best thing about the 2nd slot is the ability to mirror.

Agree! Otherwise, it almost defeats the purpose of having a back up.

Well if you follow one of the things I learned about photography, which is to try and get things as close to what you want in camera, JPEGs tend to be "close enough" as backup for certain people. Sure you won't be able to do all the crazy shadow and highlight pulls you can do with RAW, but it is there as a crutch. 
The reason why I mention this is because many people soft of use the sony A7xIII series now as a platform to poke at canikon for not including a second card slot. Well sony didn't put in a fast slot for both slots. So if you are shooting RAW on your RIII for example you will end up slowing down due to that bottleneck. So in practice a lot of people do RAW to the fast card and JPEG to the slower one. 
I have edited JPEGs before and was actually surprised to what you an do with them. A lot of the time things like wedding photography it is very much about the memories produced, and the lenses "pros" have make a major difference in the look and feel of the images. So if you were to lose your RAWs entirely (which is mostly not going to happen since even with a card failure 99% of the time 80-100% of the images are recoverable) the few JPEGs you would need to use ain't a big deal or the end of the world. You would really need to be unlucky to lose images of the first dance, or the kiss/I-do moments.