Maximum speed that the Arduino can read an SD card

Other Hardware Storage
7

Grumpy_Mike:

Serial.println(millis());

myFile.read(buf,340);
  cout << buf << endl;
  Serial.println(millis());



Is not going to tell you anything because of the time it takes to do a serial print.
Record the value of millis() in a variable, do the access. calculate the time by subtracting the recorded time before the access to the time now and then print out the result.

Thank you.
Now I see that it takes only 2 milliseconds to read the file and 11 milliseconds to open, read and close.