From owner-freebsd-questions@FreeBSD.ORG  Wed Oct 30 03:08:59 2013
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id 3F42E58A
 for <freebsd-questions@freebsd.org>; Wed, 30 Oct 2013 03:08:59 +0000 (UTC)
 (envelope-from freebsd@edvax.de)
Received: from mx01.qsc.de (mx01.qsc.de [213.148.129.14])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id 032952DD0
 for <freebsd-questions@freebsd.org>; Wed, 30 Oct 2013 03:08:58 +0000 (UTC)
Received: from r56.edvax.de (port-92-195-117-74.dynamic.qsc.de [92.195.117.74])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by mx01.qsc.de (Postfix) with ESMTPS id 62AF73C6C4;
 Wed, 30 Oct 2013 04:08:56 +0100 (CET)
Received: from r56.edvax.de (localhost [127.0.0.1])
 by r56.edvax.de (8.14.5/8.14.5) with SMTP id r9U38lma002996;
 Wed, 30 Oct 2013 04:08:47 +0100 (CET)
 (envelope-from freebsd@edvax.de)
Date: Wed, 30 Oct 2013 04:08:47 +0100
From: Polytropon <freebsd@edvax.de>
To: Olivier Nicole <olivier.nicole@cs.ait.ac.th>
Subject: Re: Intel Core 2 DUO
Message-Id: <20131030040847.24bd76e5.freebsd@edvax.de>
In-Reply-To: <CA+g+BvhuBN=-DZWEbmc=TsYw44ObsBTHM+MfcC3ff+p-9-qaBQ@mail.gmail.com>
References: <d515189f4d557ab0396ea4f5bb9c897c@dweimer.net>
 <CA+g+BvhuBN=-DZWEbmc=TsYw44ObsBTHM+MfcC3ff+p-9-qaBQ@mail.gmail.com>
Organization: EDVAX
X-Mailer: Sylpheed 3.1.1 (GTK+ 2.24.5; i386-portbld-freebsd8.2)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: FreeBSD Questions <freebsd-questions@freebsd.org>
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
Reply-To: Polytropon <freebsd@edvax.de>
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 30 Oct 2013 03:08:59 -0000

On Wed, 30 Oct 2013 10:00:27 +0700, Olivier Nicole wrote:
> Compressing a 500GB dump takes a lot of
> calculation.

I'm not sure in how far the following theoretic speculation
applies to real-world usage, but I'd like to mention it anyways.
If you add compression to an archive, this compression might
remove redundancy of data. For example, a minimal corruption
of a compressed file could have a massive impact on the data,
even up to losing the ability to uncompress it, whereas an
uncompressed archive could use the built-in redundancy to
handle the problem and still deliver the content properly.

The _kind of data_ stored may also be considered regarding
the question of compression adding any advantage (requiring
less storage space). Depending on what you backup, simply
omitting compression could reduce the processing load for
that backup, resulting in less requirements regarding CPU
and RAM (at the cost of maybe more storage space).


-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...