[colug-432] Does dd ( dcfldd ) double buffer ?

[Vince Herried]

Some time ago I asked some questions of this group about the use of the bs
option
when doing a dcfldd ( dd ) command.

I finally did some testing and the results are  inclusive :)
The input was from my hdrive
the output was to  a class 10 SD card.
I'm lead to understand that a class 10 SD card means it is good for writing
large blocks
of data. hmmm.



the data:
[root at lap3 vince]# time dcfldd statusinterval=1
if=/home/vince/Documents/
RaspberryPI/2013-05-25-wheezy-raspbian.img
of=/dev/mmcblk0
59200 blocks (1850Mb) written.
59200+0 records in
59200+0 records out

real    4m47.346s
user    0m0.367s
sys     0m3.198s
[root at lap3 vince]# time dcfldd bs=1M statusinterval=1
if=/home/vince/Documents/RaspberryPI/2013-05-25-wheezy-raspbian.img
of=/dev/mmcblk0
1850 blocks (1850Mb) written.
1850+0 records in
1850+0 records out

real    4m21.798s
user    0m0.005s
sys     0m2.155s
[root at lap3 vince]# time dcfldd bs=10M statusinterval=1
if=/home/vince/Documents/RaspberryPI/2013-05-25-wheezy-raspbian.img
of=/dev/mmcblk0
185 blocks (1850Mb) written.
185+0 records in
185+0 records out

real    4m27.242s
user    0m0.002s
sys     0m2.723s
[root at lap3 vince]# time dcfldd  statusinterval=1
if=/home/vince/Documents/RaspberryPI/2013-05-25-wheezy-raspbian.img
of=/dev/mmcblk0
59200 blocks (1850Mb) written.
59200+0 records in
59200+0 records out

real    4m27.547s
user    0m0.276s
sys     0m1.978s
[root at lap3 vince]#
-----------
Vince
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