[DRBD-user] Doubt!

Mark Watts m.watts at eris.qinetiq.com
Tue Jul 28 10:21:58 CEST 2009

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On Mon, 2009-07-27 at 10:45 -0300, Gilberto Nunes wrote:
> Hi everybody
> I have some doubt here...
> I deply two virtual server (KVM) with Ubuntu 9.04
> I had install drbd via apt-get.
> Everything is work fine...
> I had two nodes, node-A and node-B.
> I can turn node-B as primary and return node-A as a primary...
> I can mount /dev/drbd0 on node-A and node-B as well...
> But, when I write some files on node-B, on mounted /dev/drbd0, when I
> turn back node-A as a primary, on I had write on node-B do not appear on
> node-A!! :|
> I do not any ideia what is going on!!!

DRBD replicates blocks from one device to another, across a network.
It does not know anything about the filesystem, so you MUST use a
cluster-aware filesystem (GFS/GFS2 or OCFS2) if you want to mount the
DRBD device on both servers at the same time.

EXT3 is NOT cluster-aware, and you will LOOSE DATA if you try and mount
an EXT3 DRBD filesystem on both servers at the same time.

If you are just looking for Active/Passive fail-over, with a replicated
EXT3 partition, then you can use DRBD with heartbeat to achieve this.
Heartbeat will ensure that only one device has the partition mounted at
any one time.

The DRBD users guide gives comprehensive details on using DRBD with
Heartbeat: http://www.drbd.org/users-guide/ch-heartbeat.html


Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Applied Technologies
GPG Key: http://www.linux-corner.info/mwatts.gpg
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