Put your cluster in maintenance mode, if the cluster is already using DRBD:

root # crm configure edit node alice attributes maintenance="true"

If you skip this step when your cluster uses already DRBD, a syntax error in the live configuration will lead to a service shutdown.

Log in as user root.

Change DRBD's configuration files:

1. Open the file /etc/drbd.conf and insert the following lines, if they do not exist yet:

   include "drbd.d/global_common.conf";
   include "drbd.d/*.res";

   Beginning with DRBD 8.3 the configuration file is split into separate files, located under the directory /etc/drbd.d/.

2. Open the file /etc/drbd.d/global_common.conf. It contains already some pre-defined values. Go to the startup section and insert these lines:

   startup {
       # wfc-timeout degr-wfc-timeout outdated-wfc-timeout
       # wait-after-sb;
       wfc-timeout 100;
       degr-wfc-timeout 120;
   }

   These options are used to reduce the timeouts when booting, see http://www.drbd.org/users-guide-emb/re-drbdconf.html for more details.

3. Create the file /etc/drbd.d/r0.res, change the lines according to your situation, and save it:

   resource r0 { 1
     device /dev/drbd0; 2
     disk /dev/sda1; 3
     meta-disk internal; 4
     on jupiter { 5
       address  192.168.1.10:7788; 6
     }
     on venus { 5
       address 192.168.1.11:7788; 6
     }
     syncer {
       rate  7M; 7
     }
   }

   1	Name that allows some association to the service that needs them. For example, nfs, http, mysql_0, postgres_wal, etc.
   2	The device name for DRBD and its minor number. In the example above, the minor nummer 0 is used for DRBD. The udev integration scripts will give you a symlink /dev/drbd/by-res/nfs/0. Alternatively, omit the device node name in the configuration and use the following line instead: device minor 0
   3	The raw device that is replicated between nodes. Note, in this example the devices are the same on both nodes. If you need different devices, move the disk parameter into the on host.
   4	The meta-disk parameter usually contains the value internal, but it is possible to specify an explicit device to hold the meta data. See http://www.drbd.org/users-guide-emb/ch-internals.html#s-metadata for more information.
   5	The on section tells which host this configuration statement applies to.
   6	The IP address and port number of the respective node. Each resource needs an individual port, usually starting with 7788.
   7	The synchronization rate. Set it to one third of the lower of the disk- and network bandwith. It only limits the resynchronization, not the replication.

Check the syntax of your configuration file(s). If the following command returns an error, verify your files:

root # drbdadm dump all

If you have configured Csync2 (which should be the default), the DRBD configuration files are already included in the list of files which need to be synchronized. To synchronize them, use:

root # csync2 -xv /etc/drbd.d/

If you do not have Csync2 (or do not want to use it), copy the DRBD configuration files manually to the other node:

root # scp /etc/drbd.conf venus:/etc/
scp /etc/drbd.d/*  venus:/etc/drbd.d/

Initialize the meta data on both systems by entering the following on each node:

root # drbdadm create-md r0
root # systemctl start drbd.service

If your disk already contains a file system that you do not need anymore, destroy the file system structure with the following command and repeat this step:

root #  dd if=/dev/zero of=/dev/sda1 count=16 bs=1M

Watch the DRBD status by entering the following on each node:

root # systemctl status drbd.service

You should get something like this:

[... version string omitted ...]
m:res  cs         ro                   ds                         p  mounted  fstype
0:r0   Connected  Secondary/Secondary  Inconsistent/Inconsistent  C

Start the resync process on your intended primary node (jupiter in this case):

root # drbdadm -- --overwrite-data-of-peer primary r0

Check the status again with systemctl status drbd.service and after resyncronization, you get:

...
m:res  cs         ro                 ds                 p  mounted  fstype
0:r0   Connected  Primary/Secondary  UpToDate/UpToDate  C

The status in the ds row (disk status) must be UpToDate on both nodes.

Create your file system on top of your DRBD device, for example:

root # mkfs.ext3 /dev/drbd/by-res/r0/0

Mount the file system and use it:

root # mount /dev/drbd /mnt/

Reset the cluster's maintenance mode flag:

root # crm configure edit node alice attributes maintenance="false"

Start YaST and select the configuration module High Availability › DRBD. If you already have a DRBD configuration, YaST warns you. YaST will change your configuration and will save your old DRBD configuration files as *.YaSTsave.

Leave the booting flag in Start-up Configuration › Booting as it is (by default it is off); do not change that as Pacemaker manage this service.

The actual configuration of the resource is done in Resource Configuration (see Figure 15.2, “Resource Configuration”).

Figure 15.2: Resource Configuration #

Press Add to create a new resource. The following parameters have to be set twice:

All of these options are explained in the examples in the /usr/share/doc/packages/drbd/drbd.conf file and in the man page of drbd.conf(5).

If you have configured Csync2 (which should be the default), the DRBD configuration files are already included in the list of files which need to be synchronized. To synchronize them, use:

root # csync2 -xv /etc/drbd.d/

If you do not have Csync2 (or do not want to use it), copy the DRBD configuration files manually to the other node (here, another node with the name venus):

root # scp /etc/drbd.conf venus:/etc/
scp /etc/drbd.d/*  venus:/etc/drbd.d/

Initialize and start the DRBD service on both systems by entering the following on each node:

root # drbdadm create-md r0
root # systemctl start drbd.service

Configure alice as the primary node by entering the following on alice:

root # drbdsetup /dev/drbd0 primary --overwrite-data-of-peer

Check the DRBD service status by entering the following on each node:

root # systemctl status drbd.service

Before proceeding, wait until the block devices on both nodes are fully synchronized. Repeat the systemctl status drbd.service command to follow the synchronization progress.

After the block devices on both nodes are fully synchronized, format the DRBD device on the primary with your preferred file system. Any Linux file system can be used. It is recommended to use the /dev/drbd/by-res/RESOURCE name.

Test the DRBD service on jupiter.

1. Open a terminal console, then log in as root.

2. Create a mount point on jupiter, such as /srv/r0:

   root # mkdir -p /srv/r0

3. Mount the drbd device:

   root # mount -o rw /dev/drbd0 /srv/r0

4. Create a file from the primary node:

   root # touch /srv/r0/from_jupiter

5. Unmount the disk on jupiter:

   root # umount /srv/r0

6. Downgrade the DRBD service on jupiter by typing the following command on jupiter:

   root # drbdadm secondary

Test the DRBD service on venus.

1. Open a terminal console, then log in as root on venus.

2. On venus, promote the DRBD service to primary:

   root # drbdadm primary

3. On venus, check to see if venus is primary:

   root # systemctl status drbd.service

4. On venus, create a mount point such as /srv/r0mount:

   root # mkdir /srv/r0mount

5. On venus, mount the DRBD device:

   root # mount -o rw /dev/drbd_r0 /srv/r0mount

6. Verify that the file you created on jupiter exists:

   root # ls /srv/r0

   The /srv/r0mount/from_jupiter file should be listed.

If the service is working on both nodes, the DRBD setup is complete.

Set up jupiter as the primary again.

1. Dismount the disk on venus by typing the following command on venus:

   root # umount /srv/r0

2. Downgrade the DRBD service on venus by typing the following command on venus:

   root # drbdadm secondary

3. On jupiter, promote the DRBD service to primary:

   root # drbdadm primary

4. On jupiter, check to see if jupiter is primary:

   root # systemctl status drbd.service

To get the service to automatically start and fail over if the server has a problem, you can set up DRBD as a high availability service with Pacemaker/Corosync. For information about installing and configuring for SUSE Linux Enterprise 12 see Part II, “Configuration and Administration”.