[linux-lvm] Re: [OxLUG] LVM2 problems

[linux-lvm] Re: [OxLUG] LVM2 problems

[Alasdair G Kergon]

On Fri, Oct 15, 2004 at 07:28:48PM +0100, Paul Warren wrote:
> This should probably go on the linux-lvm mailing list, but the server
> seems to be down, 

Not as far as I know.

  http://sources.redhat.com/lvm2 -> linux-lvm@redhat.com

> Our primary problem is that creating snapshots occassionally hangs the
> machine.

Known issue now - unfortunately the fix involves a lot of coding and
other things have a higher priority at the moment.
 
> /lib/lvm-200/lvm vgconvert -d -v  -M1 mainvg
>     Using volume group(s) on command line
>     Finding volume group "mainvg"
>     Archiving volume group "mainvg" metadata.
> Segmentation fault
 
If it does it with the latest (2.00.25) version,
configure --enable-debug and send me the binary + core file
to investigate.

Alasdair

[linux-lvm] Re: [OxLUG] LVM2 problems

[Paul Warren]

On Fri, Oct 15, 2004 at 07:54:52PM +0100, Alasdair G Kergon wrote:
> On Fri, Oct 15, 2004 at 07:28:48PM +0100, Paul Warren wrote:
> > This should probably go on the linux-lvm mailing list, but the server
> > seems to be down, 
> 
> Not as far as I know.
> 
>   http://sources.redhat.com/lvm2 -> linux-lvm@redhat.com

Ah, thanks - I was trying:

	http://lists.sistina.com/mailman/listinfo/linux-lvm

Which I took from the bottom of (what I thought was) a recent post.

> > Our primary problem is that creating snapshots occassionally hangs the
> > machine.
> 
> Known issue now - unfortunately the fix involves a lot of coding and
> other things have a higher priority at the moment.

OK - I saw a previous post about this, but from that I wasn't sure that
it (a) killed the machine and (b) affected ext3 partitions.

> > /lib/lvm-200/lvm vgconvert -d -v  -M1 mainvg
> >     Using volume group(s) on command line
> >     Finding volume group "mainvg"
> >     Archiving volume group "mainvg" metadata.
> > Segmentation fault
>  
> If it does it with the latest (2.00.25) version,
> configure --enable-debug and send me the binary + core file
> to investigate.

OK - I'll give it a go and follow-up on linux-lvm.

thanks for the help,

Paul

Re: [linux-lvm] Re: [OxLUG] LVM2 problems

[Paul Warren]

On Fri, Oct 15, 2004 at 08:18:22PM +0100, Paul Warren wrote:
> > > /lib/lvm-200/lvm vgconvert -d -v  -M1 mainvg
> > >     Using volume group(s) on command line
> > >     Finding volume group "mainvg"
> > >     Archiving volume group "mainvg" metadata.
> > > Segmentation fault
> >  
> > If it does it with the latest (2.00.25) version,
> > configure --enable-debug and send me the binary + core file
> > to investigate.
> 
> OK - I'll give it a go and follow-up on linux-lvm.

I am now unable to reproduce this.  Instead I get the following with
both 2.00.21 and 2.00.25:

./lvm vgconvert -M1 -d -v mainvg
    Using volume group(s) on command line
    Finding volume group "mainvg"
    Archiving volume group "mainvg" metadata.
  Metadata would overwrite physical extents
  /dev/sda2: Format-specific setup of physical volume failed.
  Failed to setup physical volume "/dev/sda2"

Paul

Re: [linux-lvm] Re: [OxLUG] LVM2 problems

[Alasdair G Kergon]

On Fri, Oct 15, 2004 at 09:50:49PM +0100, Paul Warren wrote:
> ./lvm vgconvert -M1 -d -v mainvg
>   Metadata would overwrite physical extents
>   /dev/sda2: Format-specific setup of physical volume failed.
 
LVM1 needs more space for its metadata than LVM2 - this is saying
it doesn't think the LVM1 metadata will fit into the available space.

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] Re: [OxLUG] LVM2 problems

[Paul Warren]

On Fri, Oct 15, 2004 at 10:09:17PM +0100, Alasdair G Kergon wrote:
> On Fri, Oct 15, 2004 at 09:50:49PM +0100, Paul Warren wrote:
> > ./lvm vgconvert -M1 -d -v mainvg
> >   Metadata would overwrite physical extents
> >   /dev/sda2: Format-specific setup of physical volume failed.
>  
> LVM1 needs more space for its metadata than LVM2 - this is saying
> it doesn't think the LVM1 metadata will fit into the available space.

Is there any way around this?  Would growing the partition help?

The machines in question are co-located, so whilst it may be possible to
dd data off, recreate the VG and then copy it back from within an
initrd, it's not my idea of good sport, I have to say :-)

cheers,

Paul

Re: [linux-lvm] Re: [OxLUG] LVM2 problems

[Alasdair G Kergon]

On Fri, Oct 15, 2004 at 10:18:07PM +0100, Paul Warren wrote:
> Is there any way around this?  Would growing the partition help?
 
Only some careful calculations and growing it backwards
so there's the right amount of space at the start.

Otherwise you'd have to relocate the first physical extents of
data elsewhere, so you have enough unused space at the beginning 
of the disk, then edit the metadata carefully to remove
the now-unused extents and shift the start of the data to where
LVM1 expects it to be.

The tests in lib/format1/format1.c:_pv_setup() 
  /* Retain existing extent locations exactly */
check for equality because that's all there's been time to test
(and should cover most cases of lvm1->lvm2->lvm1).
Checking instead for no overlap should be sufficient but hasn't been
tested.

Alasdair
-- 
agk@redhat.com

[linux-lvm] Re: [OxLUG] LVM2 problems

[Jon Masters]

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Paul Warren wrote:

| On Fri, Oct 15, 2004 at 07:54:52PM +0100, Alasdair G Kergon wrote:

|>>Our primary problem is that creating snapshots occassionally hangs the
|>>machine.

|>Known issue now - unfortunately the fix involves a lot of coding and
|>other things have a higher priority at the moment.

| OK - I saw a previous post about this, but from that I wasn't sure that
| it (a) killed the machine and (b) affected ext3 partitions.

It's come up on a whole bunch of other mailing lists by now, including
LKML. It probably wants to be mentioned prominently on the web site.

Currently I avoid using snapshots at all, and I'm a very reserved LVM
user at the best of times - even though I think it's grrrreat. [OT] I
wish the new Debian installer supported (the only sane option)
installing LVM on md rather than having one of the other, but meh.

Look at me, I'm mailing random comments and not fixing anything, but
hey, what better way of relieving insomnia.

Jon.
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RE: [linux-lvm] Re: [OxLUG] LVM2 problems

[Kai Leibrandt]

> > > Our primary problem is that creating snapshots occassionally hangs the
> > > machine.
> >
> > Known issue now - unfortunately the fix involves a lot of coding and
> > other things have a higher priority at the moment.
>
>OK - I saw a previous post about this, but from that I wasn't sure that
>it (a) killed the machine and (b) affected ext3 partitions.

It _is_ a problem with LVM2, and for me it's totally reproducible - with 
ext3, ext2 and xfs, but only on / LV's. I am slightly saddened by the fact 
that this has low pri at the moment though :-(
I am more than willing to shoot my testbed down a few times for anyone who's 
willing to help.

Kai.

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