[DRBD-user] Best option to resize without underlying lvm?

[David Mohr]

Hi,

we have a live server running drbd 8.3.7 in primary/secondary mode. It 
has a 10tb resource configured right now, but the underlying storage 
device is 20tb big. The resource is configured directly on a raid 
partition, but we're using lvm on top of drbd.

Our initial plan was to set up a second drbd resource. But after 
reading the documentation some more, it seems like a better choice to 
keep just one resource and resize it so that drbd can better manage the 
sync traffic. If that means only using 16tb, then that's fine.

Now it's 8.3.7, so there is no volume support yet. We tried to take one 
server down and follow the offline grow instructions in the manual, but 
drbdadm complained:

root at s1a:~# drbdadm create-md vm1
> pvs stderr: /dev/sdb1: Skipping (regex)
> pvs stderr: Failed to read physical volume "/dev/sdb1"
> pvs stderr: Unlocking /var/lock/lvm/P_global
> pvs stderr: _undo_flock /var/lock/lvm/P_global
>
> md_offset 15999998881792
> al_offset 15999998849024
> bm_offset 15999510564864
>
> Found LVM2 physical volume signature
> 15624522036 kB left usable by current configuration
> Could not determine the size of the actually used data area.
>
> Device size would be truncated, which
> would corrupt data and result in
> 'access beyond end of device' errors.
> If you want me to do this, you need to zero out the first part
> of the device (destroy the content).
> You should be very sure that you mean it.
> Operation refused.
>
> Command 'drbdmeta 0 v08 /dev/sdb1 internal create-md' terminated with 
> exit
> code 40
> drbdadm create-md vm1: exited with code 40
>
I'm assuming drbd sees the lvm that is contained _within_ this resource 
and bails out.

What would be the best course of action to make the additional storage 
space available? We are trying to avoid version upgrades as much as 
possible since this is a production system (yes, I realize it was 
failure on our part to not get everything setup right away). I could 
live with upgrading drbd to 8.3.8, but we're on 2.6.34 and 8.3.8 
recommends a newer kernel.

Any advice?

Thanks,
~David