👉 : Use SD card as storage for the final ISO or extracted USB files, not as the build workspace. For building directly, an internal SSD is always faster and more reliable.
The small storage space you see is the controller's internal buffer, not your actual storage. How to Handle a Failing Card
When you buy a new card, use a free tool like (Windows) or F3 (Mac/Linux). These tools fill the card with data and verify it to ensure the capacity is real and not a "fake" card that will eventually leave you with a uupd.bin error.
