Re: [dm-crypt] LUKS & TrueCrypt - Speed Test

["Jorge Fábregas" <jorge.fabregas@gmail.com>]

On 07/28/2011 01:11 AM, Arno Wagner wrote:
> There is an old gemran egineering saying:
> 
> "wer mist mist mist" 
> 
> (along the lines of "Those who measure measure crap")
> I think it applies here.

Hello Amo,

I warned everyone that this wasn't a pro test :)  At least, I laid down
the specifics involved.


> Real-time is tricky. It does not reflect effort invested. If you 
> look at the sys itime, you see that the crypto-effort is only about
> 90 seconds more. Even that is pretty much below the measurement
> error. 

I agree here. I shouldn't have paid much attention to real time.
Nonetheless I'm still curious about the little difference...

> Very likely the differences are due to storage differences
> and do not show crypto-speed differences.


I used the same external drive for both tests.

> I suggest you run both tests at least 3 times and make sure
> your storage is significantly faster than the crypto, e.g. 
> by doing this between RAM disks or SSD storage. Also a complex
> disk access patterhn like rsync is not suitable as it may
> have complex interactions with caching and buffering.


I didn't want to go with sequential & random read/writes (with different
block sizes etc) as I wanted a rough test out of the very same tool I
use every day (rsync) with the same data on the same disk.  I understand
the crypto involved (CPU-wise) is much faster than the slow I/O of my
external drive but that's what I have.   Regarding repeating the test, I
totally agree with that.

Thanks for the input.

Regards,
Jorge