[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


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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