Yeah… I used up all 26 GB HTC One X SD storage finally. I faced my very first insufficient space alert while try install Samurai vs Zombies Defense on HTC One X. I must put lot of games, MP3, video on my HTC One X, right?
No, HTC is helping me to use up most of the HTC One X SD storage space. 16 GB of System data is caused by software bug.
How to fix HTC One X SD storage issue?
Do nothing and wait for 1.29 software update which fixed this bug. Or copy all your SD storage files to PC first. Then format HTC One X SD storage. Finally, copy those files back to HTC One X.
Or you can sell off HTC One X. And get Samsung Galaxy S III with 64 GB microSD card instead.