[dm-crypt] unusual writing speeds when benchmark speeds are high enough

.. ink .. mhogomchungu at gmail.com
Mon Mar 18 19:16:40 CET 2013


On Sun, Mar 17, 2013 at 7:07 PM, Arno Wagner <arno at wagner.name> wrote:

> On Sun, Mar 17, 2013 at 05:36:19PM -0400, .. ink .. wrote:
> > Sorry for my previous email without a title,resending the email with a
> > title this time.
> [...]
> > A user of cryptsetup(through zuluCrypt) asked me a question i can not
> > answer and asking it here.
> >
> > [root <at> sheep 8] ~ > dd if=/dev/zero of=test.img bs=70M count=1
> > 1+0 Datensätze ein
> > 1+0 Datensätze aus
> > 73400320 Bytes (73 MB) kopiert, 2,58497 s, 28,4 MB/s
> [...]
>
> Is this over USB or on an USB memory-stick? If this is a
> regular HDD, something seems to be slowing it down already.
>

In the interest of trying to figure out what speeds are "normal" i
conducted a survey in my distro(pclinuxos) forum and ask people to post
their "dd" commands and results can be seen from this thread:
http://www.pclinuxos.com/forum/index.php/topic,114335.0.html

If you go through the thread,you will see nobody went below 20MB/s.
Anything below this number is what i would consider "unusual",somebody went
above 1GB/s,that too i would consider "unusual".28MB/s is within expected
range and seem fast enough to me.One person had an unsually hight speed of
1GB/s,a few hit the 100MB/s mark and the majority are around 50MB/s +/-
30MB/s.

Maybe the disto is used by a bunch of people with old hardware(like me),or
maybe those who chose to participate use old hardware but these speeds are
not unsual to "real users" out there or atleast from users i am hearing
from.



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