From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1Ll6Li-0004Go-JG for garchives@archives.gentoo.org; Sat, 21 Mar 2009 18:55:14 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 10FFDE0453; Sat, 21 Mar 2009 18:55:13 +0000 (UTC) Received: from ey-out-1920.google.com (ey-out-1920.google.com [74.125.78.145]) by pigeon.gentoo.org (Postfix) with ESMTP id AC7BCE0453 for ; Sat, 21 Mar 2009 18:55:12 +0000 (UTC) Received: by ey-out-1920.google.com with SMTP id 4so195462eyg.10 for ; Sat, 21 Mar 2009 11:55:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:from:to:subject:date :user-agent:references:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:message-id; bh=wNr/9kXPIdBweISbZV/j6HrlOCvprQtygGZVWNg9H4I=; b=xlUCg/3q3cDGkdVV37007o7lMil5Ixi+Tp1Jp1LY2HH0CXIPCAHEh9pl/3SMzWY8E/ czU0/WVw0HL7bfKR5aa/vXQ8ltBhQ8tuC2BeLJjaKncei8oumN5D7IAJVcUoT13UVdOM YROYmNeCD1heDTy20g6h9BalC8oJSiEc7Hfmo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:subject:date:user-agent:references:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :message-id; b=ksEEiYrPtePeoTC+eldYmDEBWbIub3WcHxeBfJV8aZ6Q5XNr0vNorvp+JmKrgMcRsn BE/Eo9EKNb2VPdPueiOLxP9xy2BXclt+V49tAt00I7xranO4aiKQR6Tx5ev1ZYYGOrxk FUPMfzo24r/e+PYA5I8gcF7tPiq36giF+JGMo= Received: by 10.210.62.3 with SMTP id k3mr3936045eba.37.1237661712130; Sat, 21 Mar 2009 11:55:12 -0700 (PDT) Received: from nazgul.localnet (196-210-153-139-rrdg-esr-2.dynamic.isadsl.co.za [196.210.153.139]) by mx.google.com with ESMTPS id 28sm3720890eyg.5.2009.03.21.11.55.10 (version=SSLv3 cipher=RC4-MD5); Sat, 21 Mar 2009 11:55:11 -0700 (PDT) From: Alan McKinnon To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] extending /usr partition... Date: Sat, 21 Mar 2009 20:53:40 +0200 User-Agent: KMail/1.11.1 (Linux/2.6.28-gentoo-r3; KDE/4.2.1; x86_64; ; ) References: <49C52C76.4030609@gmail.com> <200903212012.57099.alan.mckinnon@gmail.com> <49C5344C.501@gmail.com> In-Reply-To: <49C5344C.501@gmail.com> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200903212053.40492.alan.mckinnon@gmail.com> X-Archives-Salt: 4dd9c311-c056-481f-b220-0e3cc93d37ac X-Archives-Hash: 6666bc7962eb61c3ea04573c90b6c80b On Saturday 21 March 2009 20:39:08 Jarry wrote: > Alan McKinnon wrote: > >> cp -a /mnt/gentoo/backup/var /mnt/gentoo/var > >> cp -a /mnt/gentoo/backup/usr /mnt/gentoo/usr > > > > Um, no. This gives you new usr and var directories like so: > > /usr/usr/ > > /var/var > > > > You want: > > cp -a /mnt/gentoo/backup/var /mnt/gentoo/ > > cp -a /mnt/gentoo/backup/usr /mnt/gentoo/ > > Thanks for correction! > > > With lvm, this becomes a breeze. > > I remember having lvm2 a few years ago, and despite of that I could not > extend any partition, which was being used. What is then lvm2 good for, > if I can not extend partitions on-the-fly? I can not unmount /usr before > extending... That is not lvm's fault, it is the fault of the OS. /usr is not a filesystem that changes much anyway. If you look at a few similar machines, you can guess quite accurately what it's size is going to be. /var, database directories, home directories - these are the things you can change on the fly. These are also the things that you do want to change on the fly. > And one more counter-argument: with traditional partitions I can select > where a certain partition is (physically). Those partitions accessed > frequently I put to the beginning of the disk with higher transfer-rate. > In my case, it makes quite difference: > > obelix ~ # hdparm -t /dev/md2 > Timing buffered disk reads: 252 MB in 3.02 seconds = 83.23 MB/sec > > obelix ~ # hdparm -t /dev/md9 > Timing buffered disk reads: 150 MB in 3.02 seconds = 49.72 MB/sec You have no guarantee whatsoever that the data resides on the part of the disk you think it resides on, so this entire argument becomes moot. Today, by happy coincidence, it is. Tomorrow with another drive it might not be. You also have to deal with the effect of disk caching. And you didn't do the only real test the remotely means anything at all - random writes. Throughout measurements are meaningless as the thing you measure hardly ever happens in real life. It's a lot like determining the suitability of a future wife by measuring her foot size: a perfectly correct measure, and also a perfectly useless one. It's this kind of thinking that keeps people trapped in circumstance and unable to take advantage of new ideas. In the IT industry, it is rife. -- alan dot mckinnon at gmail dot com