From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.saout.de ([127.0.0.1]) by localhost (mail.saout.de [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id fczuoVESRDba for ; Sat, 24 Nov 2012 18:39:09 +0100 (CET) Received: from mps1.wohnheimg.uni-frankfurt.de (mps1.wohnheimg.uni-frankfurt.de [141.2.118.239]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.saout.de (Postfix) with ESMTPS for ; Sat, 24 Nov 2012 18:39:09 +0100 (CET) Received: from localhost ([127.0.0.1] helo=ssl.verfeiert.org) by mps1.wohnheimg.uni-frankfurt.de via ESMTP (Exim) (envelope-from ) id 1TcJ6M-0002Ci-Sb for dm-crypt@saout.de; Sat, 24 Nov 2012 18:01:11 +0100 Message-ID: <2fffc2e10dfbf0a7ccaaf2ef43213a4e.squirrel@ssl.verfeiert.org> In-Reply-To: <20121123060720.GA5520@tansi.org> References: <50AEF7B3.4000807@babioch.de> <20121123060720.GA5520@tansi.org> Date: Sat, 24 Nov 2012 18:01:11 +0100 From: "Sven Eschenberg" MIME-Version: 1.0 Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [dm-crypt] Reconsidering default options for cryptsetup-reencrypt Reply-To: sven@whgl.uni-frankfurt.de List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: dm-crypt@saout.de On Fri, November 23, 2012 07:07, Arno Wagner wrote: > 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. > > On a side note, most HW Raids do not provide IO hinting, even worse, as a result the IO hinting is wrong, which has an impact on alignment etc., esp. when it boils down to something special like 4k sector drives. If the RAID stripes are not aligned to the 4k boundaries of the drive, and dmcrypt cannot align to the 4k boundary as well as the stripe size, you will suffer a strong degradation in performance. BTW, what exactly are you referring to, when you talk about 64 MB blocksize? > > [...] > > Arno > > -- > Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno@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 > _______________________________________________ > dm-crypt mailing list > dm-crypt@saout.de > http://www.saout.de/mailman/listinfo/dm-crypt > -Sven