Re: Moving logical volumes from one disk to another

[Pasi Pirhonen <upi iki fi>]

Hi,


On Thu, Jul 22, 2004 at 07:33:10PM -0500, Ed Wilts wrote:
> I should know this, but I need to know what steps I need to do to move a
> logical volume group from one disk to another.  The newer disk is bigger
> 
> The source is /dev/ida/c0d0p<1-3> and the target is /dev/ida/c0d1p<1-3>
> 
> I would hope that an vgextend to the new physical volume followed by an
> vgreduce but I'm not convinced that the used blocks would migrate in the
> process.
> 
> Is it as easy as dropping to single user mode and doing a dd of the
> lvm partition?  An lvm expert I'm not...
> 

I don't know if my previous knowledge about this is still valid, but
i've simutalted this years ago with IDE-disks just to make myself clear
that it's doable on environment that does have hotplugging.


So you do have c0d0p1-p3 as PVs and you's like to get all the PVs moved
and cleared out of the VG ....

You'd have like vgroot which would contain something like c0d0p1. And
you'd like to move all the blocks from that to c0d1p1 on the fly.


pvcreate the c0d1p1, cgextend that to vgroot and then just like

pvmove /dev/ida/c0d0p1 

should just like

       To move all logical extents of any logical volumes on /dev/hda4 to free
       physical extents elsewhere in the volume group, giving verbose runtime
       information, use:

            pvmove -v /dev/hda4


man page says.

When that is ready, you should be able just to vgreduce c0d0p1 from the
vgroot.


That's where linux LVM is neater than HP-(s)UX - you do have pvmore (at
least i remember that one could not say 'move all blocks from specific
device to free area' at HP-UX).


As i said, i've simulated this witl IDE-setup years ago. Getting new
disks in involved booting as getting old disk physically out, but
basically it still simulated 'the real thing' close enought that i knew
it's 'just doable'.

If this isn't clear, please ask and i'll try to say it some other,
clearer, way :)





-- 
Pasi Pirhonen - upi iki fi - http://iki.fi/upi/