It might be the slowness of that card (pasted the benchmark by Crystaldiskmark), my Evo 3D starts to lag that I have to move the application data back to the data partition of the phone's eMMC. The read write speed using A1 SD Tool is 19.33MB/s and 10.19MB/s.
I bought another Sandisk Ultra 64GB micro SD and benchmarked it using Crystaldiskmark and A1 SD Tool. The read speed using Crystaldiskmark is above 40MB/s, but the read speed tested using A1 SD Tool is 20.50MB/s. The write speed tested using A1 SD Tools is 9.17MB/s, which is even lower than the original card.
I would like to get a micro SD, maybe even a Sandisk Extreme Plus, but I am afraid that there is an IO limit on the micro SD card slot, which is a hardware limitation.
Any pointers? Thanks!