Move logical volume to a new physical disk

Question

I have three logical volumes in a single volume group using a single physical volume (the whole existing disk /dev/sda).

I now want to move one of those logical volumes to a new, faster disk, i.e., going from:

/dev/sda
    |-vg0-root → mounted to /
    |-vg0-foo  → mounted to /foo
    |-vg0-bar  → mounted to /bar

to:

/dev/sda
    |-vg0-root → mounted to /
    |-vg0-foo →  mounted to /foo

/dev/sdb
    |-vg1-bar  → mounted to /bar

From what I understand I cannot use pvmove or vgsplit because there's only one physical volume in the existing volume group.

What's a good approach to achieve this (preferably online, creating a new volume group for the new disk is not a requirement)?

I did check the many similar questions, but as far as I understand, those don't describe my situation. Bonus question: Is using a whole disk as physical volume a bad idea per se? It seems this decision made the solution much harder in my case. — htorque, Mar 8, 2015 at 9:15
Do you have any particular reason you don't want to add your new physical disk as a physical volume to the existing volume group? — Ulrich Schwarz, Mar 8, 2015 at 9:26
Not at all. If it makes things easier, the new disk can be part of vg0 as well. — htorque, Mar 8, 2015 at 9:31

Vojtech Trefny · Accepted Answer · 2022-05-17 11:17:20Z

32

One volume group solution:

 pvcreate /dev/sdb
 vgextend vg0 /dev/sdb
 pvmove -n /dev/vg0/bar /dev/sda /dev/sdb

Two volume group solution:

 pvcreate /dev/sdb
 vgcreate vg1 /dev/sdb
 lvcreate -l100%FREE vg1
 mkfs -t ext4 /dev/vg1/lvol1
 mount /dev/vg1/lvol1 /mnt

Now difficult part, all activities MUST stop on /bar:

 cd /mnt ; ( cd /bar ; tar cf - * ) | tar xf -
 cd /
 umount /mnt
 mount /dev/vg1/lvol1 /bar

where

pvcreate erase all data on disk (and prepare for LVM)
lvcreate sould create a logical volume lvol1, you specify lv name with -n bar
I use HP-UX syntax for lv, you might have to use /dev/mapper/myvg-mylv syntax

Once you have verified data are OK, in new place:

Vojtech Trefny

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answered Mar 8, 2015 at 9:42

Archemar

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Wow, seems I completely misread the pvmove man page. In that case I'll obviously settle for the one volume group solution. :)
– htorque
Mar 8, 2015 at 9:52
Actually, one could use vgsplit after pvmove to achieve the two volume group solution a bit easier (however, the logical volume still needs to be deactivated using lvchange).
– htorque
Mar 8, 2015 at 12:37
2

The usefulness of "pvmove" is a very good reason to use a single VG instead of multiple VGs.
– tgharold
Jul 5, 2015 at 23:42
2

It seems like vgreduce can then be used to remove the old volume if that is the requirement (It wasn't for the specific question, but a question asking about moving all volumes would likely be marked a duplicate)
– Gert van den Berg
Nov 15, 2016 at 13:43
My current experience is that in the single vg solution, pvmove requires an -n flag to specify the logical volume. Or it says a Physical volume /dev/vg0/bar not found Run `pvmove --help' for more information. error message. The man page says the same. May I insert it into the post?
– peterh
Sep 11, 2017 at 16:15

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