Subject: Re: Current state of Logical Volumes in NetBSD
To: Adam Hamsik <>
From: Alistair Crooks <>
List: tech-kern
Date: 11/25/2007 11:34:49
On Sun, Nov 11, 2007 at 10:17:57PM +0100, Adam Hamsik wrote:
> On Nov,Sunday 11 2007, at 12:36 PM, Alistair Crooks wrote:
> >On Sun, Nov 11, 2007 at 11:35:45AM +0100, Markus Kolb wrote:
> >I don't want to try to speak for mycroft, but my understanding of
> >his idea of wedges was that they are just simple things, which use
> >the strategy functionality to route requests to different areas
> >on the block device(s). Something crafted on top of this could provide
> >a nice, light volume manager.
> Yes, that's absolutely true. NetBSD wedges provides linear disk blocks  
> mapping same as Linux md. IMO it should be not so hard to write simple  
> volume manager for NetBSD on top of wedges. There are 3-4 options how  
> to do it:
> 1)use this years SOC code from ZFS port. I don't know if this code is  
> in useable state.
>   if not it would be good give more effort at this.
> 2)port Linux libdevmapper and lvm2 tools to netbsd on top of our  
> wedges with some support. I think that this way we keep GPL out of  
> kernel and we can use IMO really good linux lvm NetBSD volume manager.  
> Intro to Linux Lvm internals [2].
> 3) write tools + wedge device library from scratch
> I prefer 2 because of
> Pros
> a) well tested code
> b) was already done [1]
> c) I think that linux LVM is better than nothing.

Thanks for the pointers.

I wholeheartedly agree with the benefits drawn here.
> Cons
> a) add GPL stuff to netbsd base system :(
> b) too much people here hate Linux and Linux stuff :).

I disagree that too many people "hate" Linux. But some of the sources
that are mentioned are LGPL, not GPL.

But on to the meat of this mail:

Looking at reference [1] that you gave below (I missed that one, I was
on holiday at the time), I managed to get a kindly NetBSD developer to
forward me through the sources that Christian Limpach provided
pointers to.  I've brought the devmapper package up to date, and also
the lvm2 one (latest sources from  Michael van Elst
fixed an issue with the PLIST in the lvm2.  I've added Christian's
lvm.c and lvmvar.h files in the files/ subdirectory of the lvm2

I've put them up on

I'm not wedded to the idea of having these as packages, it's just the
vehicle that they came in, and because I'm fairly cognisant of the way
packages work.

I haven't tried these yet, beyond verifying that they run far enough
to complain about a non-existent directory under /var.  I haven't
tried to build a kernel with Christian's lvm driver in there either. 
What I would say is that most of the leg work to provide logical
volume management in NetBSD has been done, and it just needs a little
finishing off.  And that's where someone else (TM) comes in, because I'm
hardware constrained at the moment (even virtual hardware).

If someone would like to take these and run with them, please do - I'd
be delighted to have volume management in NetBSD.
> [1]
> [2]

Hope all this is useful - any questions, please let me know.