Subject: Re: partition bookkeeping
To: Chuck McManis <>
From: Bill Studenmund <>
List: tech-kern
Date: 10/04/1999 11:16:43
On Mon, 4 Oct 1999, Chuck McManis wrote:

> All,
> Bear with me while I ask a stupid(tm) question: 
> 	What purpose do partitions serve? 
> Even the existing system would work fine if we wrote a meta driver that did
> nothing but raw block management (think of it as a super nexus over a scsi
> driver) and then created as man virtual disk units from that sea of blocks
> for use as "drives" in the UNIX sense. Perhaps using the politically
> incorrect designation of 'vd' ( virtual disk ) and an aggregate driver of
> rd (raw disk) you could have rd0 export 100e6 raw blocks to the vd driver
> and vd0 through vd99 could each request 1e6 blocks for their use, exporting
> the standard 8 partitions if you chose (although you must admit that one
> would typically "size" the disk to be the desired size and just use the c
> partition) And it was in this point of my thinking that I wondered, "If all
> the disks were virtual disks, and they were all sized to be exactly the
> size needed, then why would we need partitions?" 
> I'll take it even further and suggest that virtual disks be growable and
> shrinkable (done several times before (to wit the Sun meta-disk-driver).
> And then go still further and suggest that the block pool be able to assign
> attributes to the blocks, qualities like "fast", "redundant", "permanent",
> and "removable."
> Raw disk devices could contribute blocks to the pool with various
> attributes and logical disk devices are constructed by fstab (or equiv)
> with pools of blocks with the desired attributes.
> Anyway, I am still wondering if rethinking the problem might not solve it
> differently.

Nope. :-)

You've basically described the logical volume manager, which IBM gave to
OSF. You might take a look at Vinum, which I think is an LVM clone. If you
want to port Vinum to NetBSD, please do so! :-)

I woldn't mind us having LVM-esque functionality (which is basically what
people are wanting with a lot of the wedge proposals). It's just there's a
big lump of work between here and there.

My question is: do we have to be stuck with 8 partitions (on all except
Amiga) until we get an LVM system working? We probably can get a (in my
opinion major) step away from 8 partitions to happen in say a month or so
(which might make 1.5). An LVM system will take a lot longer. 


Take care,