ok...when I bought my camera, I decided to buy a few XQD cards too. So to back up my files it seems crazy to put a slower Sandisk card in the other slot. Won't that slow the buffer down? Just wondering as using two different cards is a little bit confusing. I'll reach out to Jake here too for his explanation, thanks @
BackdoorHippie
It depends on how you have the 2nd slot set.
If you have it set to use slot 2 as overflow and then back up when you're not shooting (i.e. go to the menu and copy everything from the XQD card to the SD card) you'll get not just the speed of the XQD card when shooting
and the full, dedicated capacity of the buffer to feed that card.
If, however, you set it so that slot 2 gets a copy then you're taking a double hit because you're now limited by the speed of the SD card (you can get some really fast ones these days)
and hurt by a processor that must now manage 2 cards simultaneously. I've not tested how much this impacts write speeds, but I know that when I set my D610 and D750 to use the second card slot as anything other than overflow the time it took to clear the buffer almost doubled,
even if I wasn't writing anything to the second card!! That was the weirdest thing about it - set Slot 2 to JPEG but only shoot RAW and the buffer cleared slower because the code doesn't check if you're actually going to have JPEG's to write to the card, it just reserves the processing power just in case.
I roll the dice and don't back up as I shoot, but if I wanted to I'd go with scenario 1 instead of shooting to two sources simultaneously. The D500's buffer is so huge that I don't feel like firing off hundreds of shots to see the difference noted in the second scenario with the split processor. Honestly, I've never once experienced buffer clearing issues with this camera and I suspect if you have a 95Mbps SD card in the slot you'll likely never run into them unless you're looking to shoot 50+ frames in a burst and then want to do it again.