From owner-freebsd-questions@freebsd.org Fri Aug 28 17:37:47 2015 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8C4ED9C45F1 for ; Fri, 28 Aug 2015 17:37:47 +0000 (UTC) (envelope-from brandon.wandersee@gmail.com) Received: from mail-ig0-f181.google.com (mail-ig0-f181.google.com [209.85.213.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 610951138 for ; Fri, 28 Aug 2015 17:37:47 +0000 (UTC) (envelope-from brandon.wandersee@gmail.com) Received: by igui7 with SMTP id i7so21809627igu.0 for ; Fri, 28 Aug 2015 10:37:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=references:from:to:cc:subject:in-reply-to:date:message-id :mime-version:content-type; bh=+pyfbnZcax689YbsmFFrBwyLtYiUkKwokdxzGYM/QhE=; b=NE7P/1UGy5D2nCPPDI5+xuLwVEbHh/op45Nn2bdMSOaYGPjDUTb4VtoBtAbLqbalYV tMh6lFNiaVKkk0M8Q0Ig4vU5L+iB1ofzvl37PrPImziEwdtNpCxxcEljm1d4qmnQ+LFf pwBVRnavVGFYC50durWRWhwH24LxYjJt3kIBB/9Qoj+L1BgnnVwmnmNe/npEELTVd2Ts TyCMwdYBT4KczPC55mPfdAdJz/XTMLZOXycUpO2WUBXtWrtYSh2+ShoTd+Yv0BoN4rYG R3I4T+LC0m3a6HL3s9L0oXEpp6fzaL21ewlv358ofsJMbgxl/u87vLDqenNYWjMTsHjr mg4g== X-Received: by 10.50.36.106 with SMTP id p10mr4662946igj.31.1440783466211; Fri, 28 Aug 2015 10:37:46 -0700 (PDT) Received: from WorkBox.Home.gmail.com (174-30-233-239.mpls.qwest.net. [174.30.233.239]) by smtp.gmail.com with ESMTPSA id g85sm4588058iod.32.2015.08.28.10.37.44 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Aug 2015 10:37:45 -0700 (PDT) References: <55E01DAE.1020709@infracaninophile.co.uk> <20150828084643.GB1274@xtaz.uk> From: Brandon J. Wandersee To: Matt Smith Cc: Matthew Seaman , freebsd-questions@freebsd.org Subject: Re: Replacing Drive with SSD In-reply-to: <20150828084643.GB1274@xtaz.uk> Date: Fri, 28 Aug 2015 12:37:44 -0500 Message-ID: <864mjj1fh3.fsf@WorkBox.Home> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Aug 2015 17:37:47 -0000 Matt Smith writes: > I've heard a rumour that you should never use dd with SSD drives because > of the wear levelling stuff. Apparently SSDs automatically make sure > that data is sent to unused flash cells so that all the cells wear > evenly, but if you use dd on them it makes them think that every single > cell is in use which screws this up? I've read the same thing before, but I can't imagine it would really be a problem if it's the first thing you do with a new disk (and the only time you do it). Personally, though, I would just avoid using dd. If you're making a 1:1 clone of a system--if you're copying the same partition scheme to a newly purchased disk of the exact same make and model--then dd is fine, but since dd can't account for partition size or alignment, differences in block/cylinder count, filesystem settings (you should activate TRIM and eschew SU+J *before* copying a large amount of data over) and what-not, it's best to just create new partitions and filesystems and use the dump/restore method. -- ================================================================= :: Brandon Wandersee :: :: brandon.wandersee@gmail.com :: ================================================================== 'A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.' - Douglas Adams ==================================================================