From mboxrd@z Thu Jan  1 00:00:00 1970
From: Neil Brown <neilb@suse.de>
Subject: Re: Subject: [001/002 ] raid0 reshape
Date: Tue, 26 May 2009 08:14:55 +1000
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In-Reply-To: message from Goswin von Brederlow on Monday May 25
Sender: linux-raid-owner@vger.kernel.org
To: Goswin von Brederlow <goswin-v-b@web.de>
Cc: Greg Freemyer <greg.freemyer@gmail.com>, Dan Williams <dan.j.williams@intel.com>, raz ben yehuda <raziebe@013.net>, linux-raid@vger.kernel.org, Jacek Danecki <jacek.danecki@intel.com>, "Labun, Marcin" <Marcin.Labun@intel.com>
List-Id: linux-raid.ids

On Monday May 25, goswin-v-b@web.de wrote:
> Greg Freemyer <greg.freemyer@gmail.com> writes:
> 
> > ==> What I mean by raid equivalent levels
> >
> > More and more arrays allow the user to simply say "give me a 100 GB
> > logical volume with Raid 5 equivalent protection.  The array then
> > looks at the drives it has available and puts together the necessary
> > pieces.  As drives are added, removed it moves the data around under
> > its own control, but maintains the raid equivalent protection.
> >
> > Especially when working with dozens of drives and lots of logical
> > volumes it makes life much easier.  Admittedly it may come at a cost
> > of not being able to specify raid levels with the specificity that
> > mdraid currently allows.
> >
> > ==>
> >
> > The reason I ask if this is the goal is that doing so may factor into
> > decisions about how reshaping is implemented.
> >
> > Greg
> 
> That really seems to scream for LVM to support more raid levels. It
> already has linear, raid0 and raid1 support (although I have no idea
> how device mapper raid1 compares to md raid1).

Note that LVM (a suite of user-space tools) could conceivably use
md/raid1, md/raid5 etc. The functionality doesn't have to go in dm.

Neil

> 
> Those should be fleshed out more and also support raid 4/5/6 for what
> you ask.
> 
> MfG
>         Goswin