Rpi test SD card speed with hdparm

 $ hdparm -tT /dev/mmcblk0 

------------------------------------------------------------ 

@rpi4:~ $ sudo hdparm -tT /dev/sdd  (16GB class 4 SD by USB reader)
/dev/sdd:
 Timing cached reads:   1404 MB in  2.00 seconds = 702.06 MB/sec
 Timing buffered disk reads:  58 MB in  3.05 seconds =  19.03 MB/sec

------------------------------------------------------------ 

@rpi4:~ $ sudo hdparm -tT /dev/mmcblk0 (128GB SD, class 10)
/dev/mmcblk0:
 Timing cached reads:   1470 MB in  2.00 seconds = 735.12 MB/sec
 Timing buffered disk reads: 128 MB in  3.02 seconds =  42.42 MB/sec

------------------------------------------------------------ 

@rpiap:~ $ sudo hdparm -tT /dev/mmcblk0 (16GB SD Class 10)
/dev/mmcblk0:
 Timing cached reads:   874 MB in  2.00 seconds = 437.44 MB/sec
 Timing buffered disk reads:  66 MB in  3.02 seconds =  21.86 MB/sec

------------------------------------------------------------

@rpi:~ $ sudo hdparm -tT /dev/mmcblk0 (32 GB SD class 10)
/dev/mmcblk0:
 Timing cached reads:   410 MB in  2.01 seconds = 204.42 MB/sec
 Timing buffered disk reads:  66 MB in  3.04 seconds =  21.70 MB/sec

------------------------------------------------------------