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I've got a system with three drives that's build as a set of volume groups, under Ubuntu.

I'm moving the drives to my Gentoo server, which has space for all three.

Is it possible to somehow get the Gentoo box to see the existing volume groups somehow? vgscan and vgchange -a y don't seem to indicate that they see any of the volumes - is there some other sort of hackery I need to do to accomplish this?

Many thanks.

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A set of volume groups, or a set of physical volumes within a separate VG? –  Ignacio Vazquez-Abrams Dec 3 '10 at 7:45
    
I'm always confused with LVM terminology, so pardon me if I get this wrong. The three physical drives are each set up as software RAID 5. They then contain a few volume groups (I believe I had one set up as RAID5 for storage, and the other set up as RAID0 for the OS). And under that they have LV's doled out. –  Eddie Parker Dec 3 '10 at 8:37
    
Ok, so you really need to mention the RAID part in your question. That's important. –  Ryan Thompson Dec 12 '10 at 2:51
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4 Answers

You should first eliminate hardware problems as a potential cause. Fire up your partition manager of choice and verify that all the necessary drives and partitions are visible to the system.

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Sorry if I misled you. There is no hardware problems - the hard drives exist, they're visible as sd[a,b,c], and I can even boot them if I make sda the first one in the boot manager. However I don't know how to get the gentoo lvm commands to recognize the vgroups I've set up in Ubuntu previously on them. –  Eddie Parker Dec 3 '10 at 9:17
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You need to get them recognized as existing raid devices first...then vgscan should see them...
note: MAKE SURE THEY DONT GET INITAILIZED when trying to reconstruct the raid array

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What you want to do is definitely feasible.

Check that your new disks are not excluded from automatic detection in lvm.com

Also, be sure that the LVM versions are the same. There has been modifications beetween LVM1 and LVM2, which might require first to migrate on the Ubunti machine.

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up vote 0 down vote accepted

I've scored everyone up as you've all helped in some way of getting me to where I needed to be. I'm filling out this answer for completeness should anyone else ever find themselves in the same bind.

My issues were several, so I'll try and outline them:

On the new box, I failed to (in no particular order):

  1. Have the appropriate file system module available (ext4)
  2. Have the appropriate RAID kernel modules available (RAID456)
  3. Mount the software RAID devices I had created (mdadm --assemble --scan)
  4. Marked the filter in /etc/lvm/lvm.conf to accept the md device as a possible vggroup

After all that, the VG loaded fine and I am able to mount the LV that were created.

Now I just have to figure out a way to remove the miscellaneous md devices I created and merge it all into the VG... If that's possible. Expect another SuperUser question from me shortly. :)

Thanks everyone!

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