Re: [linux-lvm] Swap/DB devices (fwd)

Re: [linux-lvm] Swap/DB devices (fwd)

[Heinz Mauelshagen]

On Sat, 17 Apr 1999 01:14:00 +0100 (BST), Stephen Tweedie
<sct@redhat.com> wrote:

> 
> On Fri, 16 Apr 1999 23:47:06 METDST, Heinz Mauelshagen
> <mauelsha@ez-darmstadt.telekom.de> said:
> 
> >> I'm curious: why?  I would have thought that LVM should support any
> >> requests coming in through ll_rw_block already.
> 
> > It's simply a matter of userland (lv_create_node() and friends in lvmlib)
> > to create the LVM 'raw' device specials.
> > Only regular buffer cached device specials are created up to 0.6.
> 
> You won't need to.  The raw device patches create one single new major
> number, and let you bind the minor numbers to any block devices you
> want.  You can access _any_ block device driver without modification.
> 

The LVM lib creates the device special nodes dynamically if a logical volume
is created by lvcreate(8) or found by vgscan(8)/vgimport(8).

LVM function lv_create_node() has to be extended to create the raw device too.
The LVM driver can then be accessed by that raw device node
_without_ modification.

Heinz


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Systemmanagement C/S                             Deutsche Telekom AG
                                                 Entwicklungszentrum Darmstadt
Heinz Mauelshagen                                Otto-Roehm-Strasse 71c
Senior Systems Engineer                          Postfach 10 05 41
                                                 64205 Darmstadt
mge@ez-darmstadt.telekom.de                      Germany
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Re: [linux-lvm] Swap/DB devices

[Stephen C. Tweedie]

Hi,

On Sat, 17 Apr 1999 13:22:29 METDST, Heinz Mauelshagen
<mauelsha@ez-darmstadt.telekom.de> said:

> The LVM lib creates the device special nodes dynamically if a logical volume
> is created by lvcreate(8) or found by vgscan(8)/vgimport(8).

> LVM function lv_create_node() has to be extended to create the raw
> device too.  The LVM driver can then be accessed by that raw device
> node _without_ modification.

No, it doesn't work that way.  The major/minor numbers for the raw
devices are 100% meaningless.  Creating a raw device inode is all very
well, but it won't do anything AT ALL until you have done a raw ioctl to
bind it to a block device.

As long as you can create the LVM block devices either in some known
location or with some known block device number, you can then bind a raw
device on top without any changes to the driver underneath.

--Stephen