I have a Debian Xen DomU which has a DRBD mounted partition. I needed to resize this partition from 46G to 50G. I did the following:

  • Stopped DRBD on the secondary node: /etc/init.d/drbd stop
  • Increased the underlying LVM dist to 50 GB: lvresize -L 50G /lvm/device
  • Started DRBD again and waited for the disk to sync: /etc/init.d/drbd start
  • Switched Primaries. And performed the same on the other node.
  • Stopped drbd on the now secondary DRBD node: /etc/init.d/drbd stop
  • Increased the underlying LVM: lvresize -L 50G /lvm/device
  • Started DRBD again and waited for the disk to sync: /etc/init.d/drbd start
  • On both nodes issued: drbdadm resize drbd-device
  • On the primary node issued a: resize2fs /dev/drbd0

I get this response:

$ resize2fs 1.40-WIP (14-Nov-2006)
The filesystem is already 12058624 blocks long.  Nothing to do!

Using fdisk, both the drbd0 and the sda device drbd is using report the size of the device as 49392123904. Which is consistent with what resize2fs is saying. (12058624x4096 [blocksize]).

My issue is that df isn't reporting the change to the disk size.

$ df -B 4096
/dev/drbd0            11869420  11155652    110968 100% /data

I have done this process before and had no issues. Is there something I am missing?

  • How was it mounted? Also can you try df with --sync not sure what that does but if it is there maybe there is a reason! Also what does fdisk say? – Joshua D'Alton Mar 17 '11 at 8:14
  • This all sounds right. Does lvs report the expected size? – Insyte Mar 19 '11 at 6:16
  • perhaps remounting the partition might help? – malcolmpdx Mar 23 '11 at 23:41
  • I never figured this out. * LVS was reporting the correct size of 50G. * Unmounting and remounting the partition didn't help. * Full reboot of these DomU's also didn't solve the issue. It felt quite buggy that this wasn't working right and we were due for a hardware upgrade so I have since replaced these with 2 new CentOS machines and this is no longer an issue for me. I will however leave this question open in case someone else has similar issues. – thepearson Mar 24 '11 at 23:46

This guy wrote a nice howto about it:


  • Does following the steps in that howto actually address the issue raised in the question? – Caleb Apr 20 '11 at 11:03

You do not need to fiddle with secondary/primary roles. Just do: 1. LVM resize on both sides 2. On the primary side: drbdadm resize RESOURCE (this will also update the meta-device)

Looking at /proc/drbd should show you a resync of the new portion in progress. If this is not the case try "drbdadm adjust RESOURCE" on both sides.

Now resize the unmounted file-system using the primary side /dev/drbd/by-res/RESOURCE

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