[Flash Card Basic] What is "A1" or "A2" rating on MicroSD cards? Is it important for smartphones?

Yes, the Application Performance Class (A1 or A2) rating is specifically important for smartphones and other devices that run applications directly from the microSD card.

• Traditional SD Speed Ratings (C, U, V): These primarily focus on sequential read/write speeds, which are critical for video recording and large file transfers.
• Application Performance Class (A1/A2): This rating addresses the need for random read/write performance (IOPS - Input/Output Operations Per Second). Running apps involves many small, random read/write operations (e.g., loading app components, saving user data, accessing databases).
  • A1: Guarantees a minimum random read IOPS of 1500, random write IOPS of 500, and sustained sequential write speed of 10MB/s.
  • A2: Guarantees an even higher minimum random read IOPS of 4000, random write IOPS of 2000, and sustained sequential write speed of 10MB/s. A2 also includes host performance optimizations that can further improve app responsiveness, but these require an A2-compatible host device.
• Importance for Smartphones: If you plan to install apps, games, or even large media libraries on your smartphone's microSD card and want a smooth user experience, an A1 or especially an A2-rated card will provide significantly better performance than a card with just a C10/U1/V10 rating that lacks specific IOPS guarantees.