First of all, I'm just the messenger...don't shoot me, bro!!!  In a previous post, I asked what the SD card for the RC 2 is used for.  There weren't any answers right off the bat so I chatted with tech support and this is what I was told.  The RC 2 has a 32gb internal memory and a micro SD card slot externally.  With a card in the slot, you can't simultaneously record to the drone card and RC card.  Once you insert a card in the RC, you can power the RC up and go to Settings, Storage.  There you will be able to select whether you want to use the 32gb internal or the external SD card.  Now here's how the tech said the RC internal/card is used.  If you are recording while flying and the drone card becomes full, the data will then be transfered to the selected RC memory.  This is where my brain's logic function kicks in and questions arise.  Someone will have to do a test and see what the facts are.  When the drone card gets full, do recordings then go automatically to the drone internal memory or does that have to be selected after the card is full?  Or because you've already selected the card on the drone, does the data automatically start getting sent to the RC source previously selected (internal or card)?  I asked the tech if after the flight you could download directly from the drone card to the RC card and he said "No".  I might have gotten different answers from a different tech...who knows?  I guess I'll just have to do some tests on my own...or wait for someone else to post their results.

Hi there. Thank you for reaching out. We sincerely apologize for the confusion that caused you. I will do my best to explain to you this function.

The DJI RC 2 supports caching videos and downloading original footage of the video from the drone to the external microSD card (DJI RC 2 latest firmware now added support for saving screenshots and screen recordings when an SD card is mounted on the controller). The DJI RC 2 storage mainly focuses on caching videos, downloading original footage, and screenshots/screen recording.

When the drone card gets full, do recordings then go automatically to the drone's internal memory or does that have to be selected after the card is full?
When the microSD card is not inserted into the drone, photos/videos can only be saved in the aircraft (about 2GB) Once the aircraft storage is full, photos/videos will be saved in the RC in the form of a cache (regardless of whether the “Cache video when recording” option is enabled or not).

Please note that we can only select the storage of the drone between "Aircraft storage" or "SD Card". If no SD card is inserted into the drone which has Internal Storage, the original material is stored first in Internal Storage by default.

DJI Paladin Posted at 2-8 19:36
Hi there. Thank you for reaching out. We sincerely apologize for the confusion that caused you. I will do my best to explain to you this function.

The DJI RC 2 supports caching videos and downloading original footage of the video from the drone to the external microSD card (DJI RC 2 latest firmware now added support for saving screenshots and screen recordings when an SD card is mounted on the controller). The DJI RC 2 storage mainly focuses on caching videos, downloading original footage, and screenshots/screen recording.

When the microSD card is not inserted into the drone, photos/videos can only be saved in the aircraft (about 2GB) Once the aircraft storage is full, photos/videos will be saved in the RC in the form of a cache (regardless of whether the “Cache video when recording” option is enabled or not).

So what happens if the microSD card is inserted in the drone and the card is full?

I'm don't know what "caching" means.  Will the photos/videos that go to the RC card be full resolution...copies of the original?

Maybe you can just explain the advantage of having a microSD card in the RC.  Why would I want it and what do I do with what's on the card?

Thanks

Rustic 17, the advantage of having an sd card in the drone, is a big increase in storage capacity. From what I can see of the RC2's 32 gig storage, about half of that gets taken up by operating systems, and the rest likely gets divided up between various caches, for things like videos, screenshots, screen recordings, etc. Think of a cache as a certain amount of storage, allotted to a certain thing, like screenshots for example.
At any rate, unless you download and constantly delete the files off the RC2's internal storage, you'll run out of space pretty fast.
I put a 256 gig Sandisk extreme pro card in both my drone and RC2. It's more storage than I need, but 256 gig and up cards tend to have a faster write speed, 140 MB/s in the case of the extreme pro cards, which is plenty fast for the Mini 4 nd RC2. Honestly the 128 gig cards work fine as well, though they a have a slower write speed at 90 MB's.
The only other advantage I see in my using an SD card for storage in the RC2 is I am able to format it frequently, and avoid slower write speeds due to fragmentation. I'm not aware of any way to format the internal storage space.
What I do is after each flying session, I take the card out of the drone and put it in a card reader, I plug it into my PC and copy the files from the card into a new folder on my PC. I them eject the card from the PC, and put the card back in the drone. Then I take the RC2, power it up and plug it into my PC with a USB cable. The PC will read the controllers storage just like any drive, and I then transfer any screen recordings and screen shots into the folder on my PC, and then eject the RC2 from the PC, and remove the USB cable from the RC2. I then power up the drone and once it connects to the RC2, I use the controller to format the card on the drone, and then I format the card on my controller. I also clear my flight logs and cache, and this way I start every flying session with a clean slate and everything gets organized on the fly in my PC.
It's worth noting that if you have a card in the RC2 and have it mounted and setup, (regardless of whether you use it or the internal storage), when you pull down the menu from the top of the screen, an option called explore will appear in the pane on the left side of the pulldown thats a nice shortcut to all your files.
If you have files on the internal storage and change to using the sd card, the RC2 will ask if you want to migrate them to the card.  
I'm not sure why anyone would want to have the drone switch from using an sd card to using drone storage. I'd either just buy a big enough sd card, or keep a spare as I do. I think I paid $25 each on sale for my two 256 gig cards, so not a big expense. A fast write speed on a micro SD card is anything over 90 MB/s, with 130 or 140 being the best bang for your buck cards.
Keep in mind that on the RC2,  you're storing 1080P files at best, so 256 gigs is a lot of storage space, where as on the drone, 4K60 files will eat up storage space much faster.
Hope that is more helpful than confusing. If you have questions about what I wrote, just ask

Manitobahunter Posted at 2-8 22:57
Rustic 17, the advantage of having an sd card in the drone, is a big increase in storage capacity. From what I can see of the RC2's 32 gig storage, about half of that gets taken up by operating systems, and the rest likely gets divided up between various caches, for things like videos, screenshots, screen recordings, etc. Think of a cache as a certain amount of storage, allotted to a certain thing, like screenshots for example.
At any rate, unless you download and constantly delete the files off the RC2's internal storage, you'll run out of space pretty fast.
I put a 256 gig Sandisk extreme pro card in both my drone and RC2. It's more storage than I need, but 256 gig and up cards tend to have a faster write speed, 140 MB/s in the case of the extreme pro cards, which is plenty fast for the Mini 4 nd RC2. Honestly the 128 gig cards work fine as well, though they a have a slower write speed at 90 MB's.

I use my drone a lot traveling where I don't have access to my PC.  Instead of large 128/256 cards, I use 32gb cards which are cheap.  After each day's flights, I change out the drone card with a new one and save the cards in a safe place for when I get back home.  That way if I lose my drone in the ocean or in a crash where I can't get to it, I haven't lost all my photos/videos from the whole trip...only one day's worth.  
When you talk about screenshots and screen recordings, how do you do that on the RC 2???  I do that with my Mavic Air 2 since I'm flying using my phone, but I don't see how the RC 2 does that? Thanks for your informative reply!!!

Rustic17 Posted at 2-8 23:31
I use my drone a lot traveling where I don't have access to my PC.  Instead of large 128/256 cards, I use 32gb cards which are cheap.  After each day's flights, I change out the drone card with a new one and save the cards in a safe place for when I get back home.  That way if I lose my drone in the ocean or in a crash where I can't get to it, I haven't lost all my photos/videos from the whole trip...only one day's worth.  
When you talk about screenshots and screen recordings, how do you do that on the RC 2???  I do that with my Mavic Air 2 since I'm flying using my phone, but I don't see how the RC 2 does that? Thanks for your informative reply!!!

HI,

see pic

cheers
JJB

The best use of the SD card slot on the RC/RC2 I once saw in a YT video was: 'this is so I always have a spare card ready if the sd-card in the drone is full'....

Rustic17, just pull down with your finger from the top of the screen on the RC2, and you'll see what JJB is showing you. The area in the left pane in the pic is where you will see the Explore, just tap the word. It's currently hidden by his popup notifications. 32 gig card is fine and I understand your thinking, but they also write the slowest, you may not notice the difference, unless you try a fast one.
If you're traveling without a laptop, I beleive theres a you tube vid showing how to use an external samsung SSD drive with the RC2 to transfer things off. I have a couple 1 TB ones, but have never tried it myself.  I do however have a One Plus android phone with a USB C on the bottom and I regularly take the cards out and use a little card reader to copy vids and pics off the cards onto my phone so I can show people at the coffee shop or wherever.
If you're using 32 gig cards, make sure you format them after you copy your files off, before re using them.
I'm thinking the easist way to get a straight answer, lol.. is to fill up one of your 32 gig cards, put it back in the drone and then get out for a fun flying session and see if the controller transfers to the onboard storage.
My experience over the last few years is, although you tube videos and forums can be helpful, is I often just have to figure the drone stuff out for myself by trying things out. Plus its a excuse to go flying when I should probably be getting some work done

Rustic17 Posted at 2-8 20:27
When the microSD card is not inserted into the drone, photos/videos can only be saved in the aircraft (about 2GB) Once the aircraft storage is full, photos/videos will be saved in the RC in the form of a cache (regardless of whether the “Cache video when recording” option is enabled or not).

So what happens if the microSD card is inserted in the drone and the card is full?

Thank you for your response. We will coordinate this with our relevant team for clarification. We appreciate your patience.

Thank you for patiently waiting. If you insert a micro SD card on the aircraft and suddenly the the SD card is full, there will be a prompt message saying that the aircraft will now record in the INTERNAL STORAGE of the aircraft and after you enable it, the aircraft will first record via Internal storage of the aircraft. However, after you insert the SD card on the drone then the SD card and the internal storage are already full, there will be a prompt message again showing that the storage is full and the aircraft will now record as "Cache" and it will be saved on the DJI RC 2. Lastly, the importance of having an SD card on the DJI RC 2 is to enlarge the DJI RC 2 storage for its purposes (caching video, downloading original footage, screenshot/screen recording). Hope this helps. Have a nice day ahead.