Thanks for your quick answer.
Yes, I'm writing in C. That was actually my idea to store temporary the data stream in a buffer, and when I have enough data (one page size), write them in the SD-Card :
write (fd, buffer, PAGE_SIZE);
But I was wondering if the OS really flushes the data in one time from the virtual memory to the hardware.
Maybe a other method it to map the memory :
mem = mmap (0, PAGE_SIZE, PROT_WRITE, MAP_SHARED, PAGE_SIZE * pageCounter);
memcpy (mem, buffer, PAGE_SIZE);
munmap (mem, PAGE_SIZE);
But again, my question is the same, does the OS flush in one time from the virtual memory to the hardware ? I hope so with the MAP_SHARED flag.