SD Card Throughput exceeds - On using "dd" command

Applications Filesystems, Disks and Memory
1

Hi All,
Am using dd command to find throughput of my Normal speed SD card.
After mounting the sd card, i run,

time dd if=/dev/zero of=/mnt/sdcard/Myfile.txt bs=512
count=20480;umount /mnt/sdcard;
20480+0 records in
20480+0 records out
10485760 bytes (10 MB) copied, 0.0658825 s, 159 MB/s

real    0m0.097s
user    0m0.013s
sys     0m0.055s

But the throughput shown(159 MB/s) exceeds the normal speed of SD specification (25MB/sec).

Could you please comment on this??

Thanks,
Amio

2

Any help pls?? :frowning:

3

And when you do the same with 100MB?

4

maybe it has to do with dd's own representation of the data it's measuring: i'm not sure I really understand your program, but are you are trying to use dd to measure throughput ? I didn't know that was possible honestly. ?

5

What do you mean by "dd's own representation of the data"? The command he gave does just one thing: copy 20480*512 bytes (= 10485760 bytes = 10 MB) from /dev/zero (which always returns the \0 byte as fast as the processor can) to a file on the SD card. And AFAIK using dd to measure throughput is quite common, as it doesn't do any other stuff to the data.

It would be interesting what the numbers would be if you'd transfer 100 or 1000/1024 MB a few times.