From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id iA2FlBr30113 for ; Tue, 2 Nov 2004 10:47:11 -0500 Received: from nexredback-216-168-119-94.nexicom.net (nexredback-216-168-119-94.nexicom.net [216.168.119.94]) by mx1.redhat.com (8.12.11/8.12.11) with SMTP id iA2Fl9E8019793 for ; Tue, 2 Nov 2004 10:47:09 -0500 Message-ID: <4187ABF1.1070004@mikebabcock.ca> Date: Tue, 02 Nov 2004 10:46:57 -0500 From: "Michael T. Babcock" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Re: Software raid on top of lvm logical volume References: <41801ADE.6030308@monjoin.net> <20041028011738.GD13737@kluge.net> <41808B37.40406@monjoin.net> <20041028063530.GA13279@percy.comedia.it> <41865DE3.6040409@mikebabcock.ca> <44376.64.233.217.29.1099327893.squirrel@64.233.217.29> In-Reply-To: <44376.64.233.217.29.1099327893.squirrel@64.233.217.29> Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Erik@echohome.org, LVM general discussion and development Erik Ohrnberger wrote: >This solution would seem to be as the holy grail in that it would give you >the best of all worlds: resizable RAID storage. Or am I wrong about this >assumption? > > I've been trying to figure out a reason why it wouldn't be doable for a few weeks now. Currently, one can create RAID-0 like performance with LVM2 by specifying stripes for one's LVs. Why not: lvcreate -L 3GB --raid-level 5 --stripes 3 -n SafeData VG001 /dev/sda /dev/sdb /dev/sdc PV section 1 on sda and sdb are data, section 1 on sdc is XOR data. PV section 2 on sda and sdc are data, and XOR data on section 2 of sdb, and so on. One of the major performance implications would be the larger block sizes being dealt with; many people seem to find smaller stripes better for performance in RAID-0/5 situations, and by default one would have 4MB stripes. With some effort, I'm sure this could be rectified as well. Thoughts? Or should I blog about it instead? ;-) If I didn't have multiple out-of-town server and firewall installations this week, I'd code instead :-) -- Michael T. Babcock http://mikebabcock.ca