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Re: [linux-lvm] I need to convert my root file system to LVM (adding a 2nd disk as well).

On Wed, Apr 25, 2001 at 01:03:29PM -0400, Rupert Heesom wrote:
> On 25 Apr 2001 08:35:38 +0100, Patrick Caulfield wrote:
> > On Tue, Apr 24, 2001 at 11:39:02AM -0400, Rupert Heesom wrote:
> > If you're not very familiar with LVM I recommend you have a play with it on the
> > new disk before attempting to convert the root filesystem though.
> I'm playing around with LVM on my 2nd spare disk (/dev/sdb).
> The partitions are that disk now are -
> /dev/sdb1, /dev/sdb2
> I've created Vol Grp "vg" (/dev/vg), and Log Vol "lvol1"
> (/dev/vg/lvol1).
> I'm now trying to take one of the partitions out of the LV.  I'm hoping
> that I can run a command something like lvreduce /dev/sdb2 lvol1 (reduce
> lvol1 by taking /dev/sdb2 out of the vol), but the only way I can see of
> reducing lvol1 is by specifying the Mbs to reduce the LV by.   If I do
> this (specify the size of /dev/sdb2), how do I know that the LV will
> give it's space back to /dev/sdb2?
> It could easily give space back to /dev/sdb1 as well.
> The part in the HOWTO about removing an old disk should help, but it
> doesn't.  It talks about vgextending to add the new disk into the VG,
> then vgreducing to take the old disk out of the VG.
> When I try to "vgreduce vg /dev/sdb2", I'm told that /dev/sdb2 is still
> active.
> How do I de-activate /dev/sdb2?
> I think I'm getting the idea of all this slowly, but am still pretty
> confused overall!!

What you need to do is lvreduce the volume to the size of the PV /dev/sdb1
(which will be slightly smaller than the actual partition), then use pvmove to
move the used extents from sdb2 to sdb2. *then* you can vgreduce vg /dev/sdb2.

That might sound a little over-complicated but it's really the more common case
in "real world" situations to be LV focussed rather than PV focussed. (I think!)


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