From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id jB9IXsV28277 for ; Fri, 9 Dec 2005 13:33:54 -0500 Received: from eastrmmtao02.cox.net (eastrmmtao02.cox.net [68.230.240.37]) by mx3.redhat.com (8.13.1/8.13.1) with ESMTP id jB9IXhv7013637 for ; Fri, 9 Dec 2005 13:33:43 -0500 Received: from [192.168.0.9] (really [70.179.95.46]) by eastrmmtao02.cox.net (InterMail vM.6.01.05.02 201-2131-123-102-20050715) with ESMTP id <20051209183214.OQBW8508.eastrmmtao02.cox.net@[192.168.0.9]> for ; Fri, 9 Dec 2005 13:32:14 -0500 Message-ID: <4399CE19.80601@cox.net> Date: Fri, 09 Dec 2005 13:34:01 -0500 From: Old Fart MIME-Version: 1.0 Subject: Re: [linux-lvm] If one disk fails i loose everything? References: <439620CE.1030902@ee.duth.gr> <8777.208.178.77.200.1134146221.squirrel@mnementh.dragonhold.org> In-Reply-To: <8777.208.178.77.200.1134146221.squirrel@mnementh.dragonhold.org> Content-Transfer-Encoding: 7bit Reply-To: rascal.jumper-747@cox.net.spamorama.redhat.com, 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: LVM general discussion and development gwood@dragonhold.org wrote: > In the answers below I've taken 'one linear volume group' to actually mean > 'one linear volume using all the space in the volume group'. If this is > not what you meant, can you please describe your setup? > > >> 1. If one hard disk fails (hardware) do I loose all the data stored on >> the VG? >> > I'm not sure where you searched, but the answer to this is a fundamental > characteristic of RAID0 - there is no redundancy. If you have a concat > (rather than a stripe), then you /might/ be able to salvage /some/ data - > but the chances are pretty slim that you'll get anything sane back out of > it, and you're going to have to do some relatively low level stuff to do > even that I would have thought. > > >> 2. Can I add a new hard disk in the VG without having to format it >> before? (I mean if it is full of data can I just add it?) >> > Not easily using LVM on linux, no. If it already has partitions on it, > then the layout of the data on the drive is incorrect for LVM. There may > be tools out there to overlay the required metadata, but the underlying > partitions will have to reduce in size, so this would require the > filesystems to support being shrunk. > > >> 3. In case of failure can I recover the data from a single disk on >> another box? >> > What sort of failure? Any VG that has enough drives to provide you with a > working volume group/volume can be imported to another machine and read. > So if you have 3 volumes over the VG, and only one of them doesn't have a > complete set of blocks on it - the other 2 can be salvaged. In the case > of the arrangement you're talking about, no. > > If you need to be able to recover the data, then a simple linear volume > (with no redundancy) is not a good idea. > > (In answer to the subject line, 'with the arrangement you're talking > about' - YES') > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ > > Good discussion....the need to protect data under various contingencies is why I use raid5 sets as the PVs. You can lose up to two and keep your data, hot add, have spares, etc. -- Regards, Old Fart