measuring the transfer rate of the sd card

Create a directory on the mounted sd card:

mkdir /mmc/speedtest
cd /mmc/speedtest

Copy the following files on the sd card:

/mmc/speedtest/mmcspeedtest
/mmc/speedtest/mmcspeedtest_schreiben
/mmc/speedtest/mmcspeedtest_lesen

Make the files executable:

chmod +x /mmc/speedtest/mmcspeedtest
chmod +x /mmc/speedtest/mmcspeedtest_schreiben
chmod +x /mmc/speedtest/mmcspeedtest_lesen

Now start the test with ./mmcspeedtest.

My result was about 1 minute and 10 seconds for write and read each.
32 MB of data are getting written and readed.
32768 kyByte / time in seconds = your speed in kByte/sec

mounting the sd card to the root directory