I am experiencing very low read and write speeds (near 4.5MB/S) on my high-speed Sandisk Extreme 64GB U3 A2 SD card (the card was validated on an external card reader, achieving a write speed of 85MB/s).
I am expecting to get SD card R/W speeds close to 25MB/s when running on the Duo256m.
I arrived at this test after setting up a web server and noticing the low download speed. Initially, I thought the issue was with Ethernet, but it seems that the problem is with the SD card access, which is slowing everything down.
[root@milkv-duo]~# dd if=/dev/zero of=/root/pepe.test bs=100M count=2 oflag=direct
2+0 records in
2+0 records out
209715200 bytes (210 MB, 200 MiB) copied, 46.4414 s, 4.5 MB/s
and
[root@milkv-duo]~# dd if=/dev/mmcblk0 of=/dev/null bs=4M count=256 iflag=direct
228+0 records in
227+0 records out
952107008 bytes (952 MB, 908 MiB) copied, 200.711 s, 4.7 MB/s