How fast is a SD page read from a file?
So my question: is 20 ms enough to read like 50 pages of 512 bytes from an SD card which are located on different (but known) file offsets within a 2+ MB file?


Let us do the numbers: 50 * 512 = 25 Kbyte in 20 ms is 1.25 Mbyte/s. As the max speed for SPI is 1 Mbyte/s (on Arduino AVR, 16 MHz) we do not have to go any further. The answer is: No.

Cheers!