Re: [linux-lvm] software RAID over LVM

From: Austin Gonyou <austin@coremetrics.com>
To: linux-lvm@sistina.com
Subject: Re: [linux-lvm] software RAID over LVM
Date: Wed Jan 30 11:55:04 2002	[thread overview]
Message-ID: <1012413308.12412.3.camel@UberGeek> (raw)
In-Reply-To: <3C5831E7.9060705@birddog.com>

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I was stating that it's the way you'd want to do that. Doing otherwise
would be bad. :) 

On Wed, 2002-01-30 at 11:48, Kirby C. Bohling wrote:
> Austin,
> 
> 	Just as an aside, I have done all of those configurations with
> no LVM 
> involved.  RAID0+1, RAID1+0, and RAID5 on top of mirrored devices.  Yes 
> RAID1+0 isn't very smart, but we did it.  It is much simpiler, and more 
> reliable to have RAID underneath LVM.  Not because LVM is unreliable, 
> but if you forget, or don't realize both halves of a mirror got migrated
> 
> to the same disks your mirror might be a lot less redundant then you 
> believe it is.  Wow, I just restated the a FAQ entry in a very poor 
> manner...
> 
> 	LVM didn't try to be all incompassing.  It could have been, but
> it would 
> have made things more complicated and duplicated a bunch of work from 
> what I have read on this list.
> 
> 		Kirby
> 
> 
> Austin Gonyou wrote:
> > I can think of MANY uses for this. The main one would be a relatively
> > cheap way of making a RAID0+1, or stripe of mirrors. If you don't have
> > any hardware to do this with, then software is next. It'd be nice to
> be
> > able to do this, for sure. You could even do 0+5, or something crazy
> > like that too.
> > 
> > 
> > On Tue, 2002-01-29 at 17:50, Kirby C. Bohling wrote:
> > 
> >>Paul,
> >>
> >>	I haven't done it.  I have done mirrors underneath, but I am
> >>curious what 
> >>is the reasoning and/or application.  The only thing I can think up is
> 
> >>so you can migrate your mirrors to faster drives easily.  However, 
> >>putting the mirror underneath should allow you to move off one mirror 
> >>onto another.
> >>
> >>	I don't believe that mirroring can be expanded like a filesystem
> >>can.  In 
> >>order to make the mirror bigger, you have to break the mirror as far
> as 
> >>I know.  So what are you planning on doing with it, or is it just "to 
> >>see if it could be done".
> >>
> >>	Thanks,
> >>		Kirby
> >>
> >>lvm@agilecat.mailshell.com wrote:
> >>
> >>>Hi all,
> >>>
> >>>I understand the use of LVM over software RAID.
> >>>But is it possible to use software RAID ON TOP
> >>>of LVM?  For example, have a RAID-1 mirroring
> >>>array created from two logical volumes.
> >>>
> >>>I've tried and it seems to be working.  Is
> >>>it safe to do this?  Any pitfalls?
> >>>
> >>>Thanks!
> >>>
> >>>Paul
> >>>
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> >>>
> >>>
> >>
> >>
> >>_______________________________________________
> >>linux-lvm mailing list
> >>linux-lvm@sistina.com
> >>http://lists.sistina.com/mailman/listinfo/linux-lvm
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> >>
> 
> 
> 
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-- 
Austin Gonyou
Systems Architect, CCNA
Coremetrics, Inc.
Phone: 512-698-7250
email: austin@coremetrics.com

"It is the part of a good shepherd to shear his flock, not to skin it."
Latin Proverb

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