[dm-crypt] Reconsidering default options for cryptsetup-reencrypt

Arno Wagner arno at wagner.name
Fri Nov 23 07:07:20 CET 2012


On Fri, Nov 23, 2012 at 05:12:35AM +0100, Karol Babioch wrote:
> Hi,
> 
> I'm currently reencrypting my (hardware) RAID setup, which is quite big
> (12 TB) in order to change the cipher from aes-xts-plain to aes-xts-plain64.
> 
> While playing around with various options, I found out that a block size
> of 64 MB and the use of direct I/O results in the highest speed for me.

This seems to be RAID options (i.e. out-of-scope for cryptsetup), and 
very specific ones as you have some hardware RAID solution. Also 64MB 
block size is very, very large and will be a problem for some workloads.
 
Also, your sped gain of 10% is negligible, as it is likely not robust 
and very much dependent on the workload.

[...]
> Maybe I'm just generalizing too much here when trying
> to come up with some conclusions based on my hardware.

I think you do. I also think that HW raid is a bit exotic on Linux
these days, as SW RAID gives better features and often better
performance.

Arno

--
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
One of the painful things about our time is that those who feel certainty
are stupid, and those with any imagination and understanding are filled
with doubt and indecision. -- Bertrand Russell


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