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I'm going to add drbd to an existing LVM, I want to keep LVM data. I follow this post:

what I already did

  • stopped kvm virtual machine using LVM

  • backup of LVM data with dd

    dd if=/dev/server1_vg0/res of=/root/res.dump bs=512K
  • config file for drbd resource

    resource res {
      device    /dev/drbd1;
      disk      /dev/server1_vg0/res;
      flexible-meta-disk internal;
      on server1 {
        address   x.x.x.x:xxxx;
      on server2 {
        address   x.x.x.x:xxxx;
  • growed 5MB LVM to fit drbd metadata

    lvextend -L +5m /dev/server1_vg0/res

Now I see this warning when I do

[root@server1 ~]# drbdadm create-md res
md_offset 21483220992
al_offset 21483188224
bm_offset 21482528768

Found some data

 ==> This might destroy existing data! <==

Do you want to proceed?
[need to type 'yes' to confirm]    

Operation canceled.

will this command destroy LVM data? what those offsets mean? (md/al/bm_offset)

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up vote 0 down vote accepted

It was safe to do:

LV ending before adding 5MB:

[root@server1 ~]# blockdev --getsize64 /dev/server1_vg0/res

so, all drbd offsets start after LV data, I proceeded and it worked fine

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