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-   -   Resizing physical volume for lvm. (http://www.linux-archive.org/gentoo-user/268035-resizing-physical-volume-lvm.html)

Alan McKinnon 03-22-2009 07:35 PM

Resizing physical volume for lvm.
 
On Sunday 22 March 2009 22:15:14 Momesso Andrea wrote:
> My current setup is:
>
> Device Boot Start End Blocks Id System
> /dev/sda1 * 1 2894 23246023+ 83 Linux
> /dev/sda2 2895 3381 3911827+ 82 Linux
> swap /Solaris
> /dev/sda3 3382 24804 172080247+ 83 Linux
> /dev/sda4 24805 30401 44957902+ 83 Linux
>
> where sda3 is an lvm volume and sda4 is free space.
>
> I'd like to to merge sda3 and sda4 into a single partition without
> losing the data on it, but I'm not sure if it is possible.
>
> My guess is that I can use fdisk to delete sda4 and sda3, create a sda3
> partition starting at 3382 and ending at 30401, then use pvresize to
> enlarge it.

Correct. That's all there is to it.

> This is from man pvresize:
> "Expand the PV on /dev/sda1 after enlarging the partition with fdisk:
> pvresize /dev/sda1"
>
> Is that going to work or I'm going to lose all the data?

Your data is safe if you do exactly the steps you said above.

Caveat: I have no idea why this doesn't work, but if you make sda4 an extended
partition and create sda5 as a logical with exactly the same start and end as
you describe above, you do in fact lose all data. Obviously there is a
difference between a physical and a logical partition with the same location,
but I don't know why this is.

Which is a pity, as 4 logical partitions is a little too constrictive, I
prefer the extra freedom to move things around with extended partitions.

> P.S. I'm not using vgextend to simply add sda4 to the lvm because I
> might want to migrate my root (sda1) to ext4, and to do so I will need
> to split it in two separate partitions (/boot using ext3 and / using
> ext4). This way I'm not going to need extended partitions.

ext3 on /boot is pointless. The ext3 metadata takes up a considerable chunk of
the space on a typical /boot, for no good reason at all - writes to it are
exceptionally rare so there's no real-worlld benefit to the journal.

Ext2 is ideal for /boot.


--
alan dot mckinnon at gmail dot com

Dirk Heinrichs 03-22-2009 07:39 PM

Resizing physical volume for lvm.
 
Am Sonntag, 22. März 2009 21:15:14 schrieb Momesso Andrea:
> P.S. I'm not using vgextend to simply add sda4 to the lvm because I
> might want to migrate my root (sda1) to ext4

Why do want to do that? ext4 is just a couple of months old and there's no
proof of stability whatsoever for it. Better try it with uncritical data
partitions (portage tree, distfiles) first.

Bye...

Dirk

Momesso Andrea 03-22-2009 07:42 PM

Resizing physical volume for lvm.
 
On Sun, 22 Mar 2009 22:35:35 +0200
Alan McKinnon <alan.mckinnon@gmail.com> wrote:

> On Sunday 22 March 2009 22:15:14 Momesso Andrea wrote:
> > My current setup is:
> >
> > Device Boot Start End Blocks Id System
> > /dev/sda1 * 1 2894 23246023+ 83 Linux
> > /dev/sda2 2895 3381 3911827+ 82 Linux
> > swap /Solaris
> > /dev/sda3 3382 24804 172080247+ 83 Linux
> > /dev/sda4 24805 30401 44957902+ 83 Linux
> >
> > where sda3 is an lvm volume and sda4 is free space.
> >
> > I'd like to to merge sda3 and sda4 into a single partition without
> > losing the data on it, but I'm not sure if it is possible.
> >
> > My guess is that I can use fdisk to delete sda4 and sda3, create a
> > sda3 partition starting at 3382 and ending at 30401, then use
> > pvresize to enlarge it.
>
> Correct. That's all there is to it.
>
> > This is from man pvresize:
> > "Expand the PV on /dev/sda1 after enlarging the partition with
> > fdisk: pvresize /dev/sda1"
> >
> > Is that going to work or I'm going to lose all the data?
>
> Your data is safe if you do exactly the steps you said above.

Good to know! In any case backups are available, but I prefer not to
use them if not necessary.

>
> Caveat: I have no idea why this doesn't work, but if you make sda4 an
> extended partition and create sda5 as a logical with exactly the same
> start and end as you describe above, you do in fact lose all data.
> Obviously there is a difference between a physical and a logical
> partition with the same location, but I don't know why this is.
>
> Which is a pity, as 4 logical partitions is a little too
> constrictive, I prefer the extra freedom to move things around with
> extended partitions.
>
> > P.S. I'm not using vgextend to simply add sda4 to the lvm because I
> > might want to migrate my root (sda1) to ext4, and to do so I will
> > need to split it in two separate partitions (/boot using ext3 and /
> > using ext4). This way I'm not going to need extended partitions.
>
> ext3 on /boot is pointless. The ext3 metadata takes up a considerable
> chunk of the space on a typical /boot, for no good reason at all -
> writes to it are exceptionally rare so there's no real-worlld benefit
> to the journal.
>
> Ext2 is ideal for /boot.
>
Thanks for the advice. Will be a problem for lvm if I add a partition
before it? I mean, will I need to change any config files while lvm is
gonna reside on sda4 instead of sda3?

---
TopperH
http://topperh.blogspot.com

Momesso Andrea 03-22-2009 07:46 PM

Resizing physical volume for lvm.
 
On Sun, 22 Mar 2009 21:39:29 +0100
Dirk Heinrichs <dirk.heinrichs@online.de> wrote:

> Am Sonntag, 22. März 2009 21:15:14 schrieb Momesso Andrea:
> > P.S. I'm not using vgextend to simply add sda4 to the lvm because I
> > might want to migrate my root (sda1) to ext4
>
> Why do want to do that? ext4 is just a couple of months old and
> there's no proof of stability whatsoever for it. Better try it with
> uncritical data partitions (portage tree, distfiles) first.
>
> Bye...
>
> Dirk

Don't want to do that right now, but I like to have things set up to
create me less problems as possible when I will decide to do the
migration.

In any case I don't consider the root partition of my laptop to be
really critical. I'm not planning any migration in /home, that will
remain ext3.

---
TopperH
http://topperh.blogspot.com

Neil Bothwick 03-22-2009 07:49 PM

Resizing physical volume for lvm.
 
On Sun, 22 Mar 2009 21:39:29 +0100, Dirk Heinrichs wrote:

> > P.S. I'm not using vgextend to simply add sda4 to the lvm because I
> > might want to migrate my root (sda1) to ext4
>
> Why do want to do that? ext4 is just a couple of months old and there's
> no proof of stability whatsoever for it. Better try it with uncritical
> data partitions (portage tree, distfiles) first.

Yet if you do, the latest GRUB boots from ext4 partitions, so you don't
need to separate /boot.


--
Neil Bothwick

"I'm Not Sure If I'm Homosexual", Said Tom, Half In Earnest.

Momesso Andrea 03-22-2009 07:58 PM

Resizing physical volume for lvm.
 
On Sun, 22 Mar 2009 20:49:36 +0000
Neil Bothwick <neil@digimed.co.uk> wrote:

> On Sun, 22 Mar 2009 21:39:29 +0100, Dirk Heinrichs wrote:
>
> > > P.S. I'm not using vgextend to simply add sda4 to the lvm because
> > > I might want to migrate my root (sda1) to ext4
> >
> > Why do want to do that? ext4 is just a couple of months old and
> > there's no proof of stability whatsoever for it. Better try it with
> > uncritical data partitions (portage tree, distfiles) first.
>
> Yet if you do, the latest GRUB boots from ext4 partitions, so you
> don't need to separate /boot.
>
>

I heard it can boot from ext4 using a patch that is not 100% safe...
Does anyone have positive (or negative) experience with that?

---
TopperH
http://topperh.blogspot.com

Momesso Andrea 03-22-2009 08:00 PM

Resizing physical volume for lvm.
 
On Sun, 22 Mar 2009 22:35:35 +0200
Alan McKinnon <alan.mckinnon@gmail.com> wrote:

> On Sunday 22 March 2009 22:15:14 Momesso Andrea wrote:
> > My current setup is:
> >
> > Device Boot Start End Blocks Id System
> > /dev/sda1 * 1 2894 23246023+ 83 Linux
> > /dev/sda2 2895 3381 3911827+ 82 Linux
> > swap /Solaris
> > /dev/sda3 3382 24804 172080247+ 83 Linux
> > /dev/sda4 24805 30401 44957902+ 83 Linux
> >
> > where sda3 is an lvm volume and sda4 is free space.
> >
> > I'd like to to merge sda3 and sda4 into a single partition without
> > losing the data on it, but I'm not sure if it is possible.
> >
> > My guess is that I can use fdisk to delete sda4 and sda3, create a
> > sda3 partition starting at 3382 and ending at 30401, then use
> > pvresize to enlarge it.
>
> Correct. That's all there is to it.
>
> > This is from man pvresize:
> > "Expand the PV on /dev/sda1 after enlarging the partition with
> > fdisk: pvresize /dev/sda1"
> >
> > Is that going to work or I'm going to lose all the data?
>
> Your data is safe if you do exactly the steps you said above.
>
pvresize /dev/sda3
/dev/sda3: too many metadata areas for pvresize

Looks like I cannot expand it...

---
TopperH
http://topperh.blogspot.com

Albert Hopkins 03-22-2009 08:39 PM

Resizing physical volume for lvm.
 
On Sun, 2009-03-22 at 21:58 +0100, Momesso Andrea wrote:
> On Sun, 22 Mar 2009 20:49:36 +0000
> Neil Bothwick <neil@digimed.co.uk> wrote:
>
> > On Sun, 22 Mar 2009 21:39:29 +0100, Dirk Heinrichs wrote:
> >
> > > > P.S. I'm not using vgextend to simply add sda4 to the lvm because
> > > > I might want to migrate my root (sda1) to ext4
> > >
> > > Why do want to do that? ext4 is just a couple of months old and
> > > there's no proof of stability whatsoever for it. Better try it with
> > > uncritical data partitions (portage tree, distfiles) first.
> >
> > Yet if you do, the latest GRUB boots from ext4 partitions, so you
> > don't need to separate /boot.
> >
> >
>
> I heard it can boot from ext4 using a patch that is not 100% safe...
> Does anyone have positive (or negative) experience with that?

You don't need to apply any patch; it comes with GRUB. I didn't get any
"WARNING: this patch will fuck your box" messages when I installed it.
In my experience I haven't seen any difference between it and the 25 or
so other patches that Gentoo applies to GRUB.

Alan McKinnon 03-23-2009 06:16 AM

Resizing physical volume for lvm.
 
On Sunday 22 March 2009 22:42:39 Momesso Andrea wrote:
> Thanks for the advice. Will be a problem for lvm if I add a partition
> before it? I mean, will I need to change any config files while lvm is
> gonna reside on sda4 instead of sda3?

It's not a problem. LVM scans the drive looking for pvs and uses them as it
finds them. You can see this behaviour when running 'vgchange -a y'. It
doesn't need or really use the partition number at all.

You may have such things in lvm config files somewhere. If it becomes
problematic, simply remove/comment those entries.

--
alan dot mckinnon at gmail dot com

Alan McKinnon 03-23-2009 06:22 AM

Resizing physical volume for lvm.
 
On Sunday 22 March 2009 23:00:07 Momesso Andrea wrote:
> On Sun, 22 Mar 2009 22:35:35 +0200
>
> Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> > On Sunday 22 March 2009 22:15:14 Momesso Andrea wrote:

> > Your data is safe if you do exactly the steps you said above.
>
> pvresize /dev/sda3
> /dev/sda3: too many metadata areas for pvresize
>
> Looks like I cannot expand it...

This code commit is giving the error:

http://sources.redhat.com/ml/lvm2-cvs/2008-09/msg00001.html

and a solution can be found in this thread (courtesy of that nice man Mr.
Google):

http://archives.free.net.ph/message/20081129.151331.dd8edce0.en.html
>
> ---
> TopperH
> http://topperh.blogspot.com

--
alan dot mckinnon at gmail dot com


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