Just to clarify a bit more - those speeds are raw block device speeds. Filesystem brings overhead so real numbers when creating/copying files may be slower (significantly in some cases).


Here are tests I just made on N800 running OS2007 with Transcend 150x 4GB SD card.

Nokia-N800-26:~# sync ; time sh -c 'dd if=/dev/zero of=/media/mmc1/testfile bs=102400 count=1024; sync'
1024+0 records in
1024+0 records out
real 0m 19.60s
user 0m 0.00s
sys 0m 1.45s
Nokia-N800-26:~# ls -l /media/mmc1/testfile
-rwxr-xr-x 1 user root 104857600 Aug 4 22:31 /media/mmc1/testfile
Nokia-N800-26:~# sync ; time sh -c 'dd if=/dev/zero of=/media/mmc1/testfile2 bs=1024 count=102400; sync'
102400+0 records in
102400+0 records out
real 0m 31.80s
user 0m 0.20s
sys 0m 3.64s
Nokia-N800-26:~# sync ; time sh -c 'dd if=/dev/zero of=/media/mmc1/testfile2 bs=102400 count=1024; sync'
1024+0 records in
1024+0 records out
real 0m 19.38s
user 0m 0.00s
sys 0m 1.63s
Nokia-N800-26:~# sync ; time sh -c 'dd if=/dev/zero of=/media/mmc1/testfile2 bs=4096 count=25600; sync'
25600+0 records in
25600+0 records out
real 0m 19.65s
user 0m 0.01s
sys 0m 2.05s

all tests created 100MB file on FAT partition. With block size 1024 bytes speed is ~3MB/s, with block size 4096 and up speed is ~5MB/s. This includes filesystem overhead.

Here is raw block device writing speed (zeroing 100MB beginning of first partition)

Nokia-N800-26:~# sync ; time sh -c 'dd of=/dev/mmcblk1p1 if=/dev/zero bs=102400 count=1024 ; sync'
1024+0 records in
1024+0 records out
real 0m 10.23s
user 0m 0.01s
sys 0m 1.28s

100MB in 10 seconds

and finally restoring data to mmcblk1p1 partition from file on mmcblk0p4 formatted as ext2
Nokia-N800-26:~# sync ; time sh -c 'dd of=/dev/mmcblk1p1 if=/SD4GB bs=102400 count=1024 ; sync'
1024+0 records in
1024+0 records out
real 0m 18.80s
user 0m 0.03s
sys 0m 2.56s

5MB/s raw write speed while reading real data from other mmc card