Procedure 15.1. Manually Configuring DRBD¶

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

   root # crm configure property maintenance-mode=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.

2. Log in as user root.

3. 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          # wfc-timeout degr-wfc-timeout outdated-wfc-timeout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 { 
        device /dev/drbd0; 
        disk /dev/sda1; 
        meta-disk internal; 
        on alice { 
          address  192.168.1.10:7788; 
        }
        on bob { 
          address 192.168.1.11:7788; 
        }
        syncer {
          rate  7M; 
        }
      }

      	Name that allows some association to the service that needs them. For example, nfs, http, mysql_0, postgres_wal, etc.
      	The device name for DRBD and its minor number. In the example above, the minor number 0 is used for DRBD. The udev integration scripts will give you a symbolic link /dev/drbd/by-res/nfs/0. Alternatively, omit the device node name in the configuration and use the following line instead: drbd0 minor 0 (/dev/ is optional) or /dev/drbd0
      	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.
      	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.
      	The on section states which host this configuration statement applies to.
      	The IP address and port number of the respective node. Each resource needs an individual port, usually starting with 7788.
      	The synchronization rate. Set it to one third of the lower of the disk- and network bandwidth. It only limits the resynchronization, not the replication.

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

   root # drbdadm dump all

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:

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

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

   root # drbdadm create-md r0
   root # rcdrbd start

   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

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

   root # rcdrbd status

   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

8. Start the resync process on your intended primary node (alice in this case):

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

9. Check the status again with rcdrbd status and 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.

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

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

11. Mount the file system and use it:

    root # mount /dev/drbd /mnt/

12. Reset the cluster's maintenance mode flag:

    root # crm configure property maintenance-mode=false

Procedure 15.2. Using YaST to Configure DRBD¶

1. 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 manages this service.

2. 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 need to be set twice:

   Resource Name	The name of the resource (mandatory)
   Name	The host name of the relevant node
   Address:Port	The IP address and port number (default 7788) for the respective node
   Device	The block device path that is used to access the replicated data. If the device contains a minor number, the associated block device is usually named /dev/drbdX, where X is the device minor number. If the device does not contain a minor number, make sure to add minor 0 after the device name.
   Disk	The device that is replicated between both nodes.
   Meta-disk	The Meta-disk is either set to the value internal or specifies an explicit device extended by an index to hold the meta data needed by DRBD. A real device may also be used for multiple drbd resources. For example, if your Meta-Disk is /dev/sda6[0] for the first resource, you may use /dev/sda6[1] for the second resource. However, there must be at least 128 MB space for each resource available on this disk. The fixed metadata size limits the maximum data size that you can replicate.

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

3. 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 bob):

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

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

   root # drbdadm create-md r0
   root # rcdrbrd start

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

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

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

   rcdrbd status

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

7. 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.

1. Test the DRBD service on alice.

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

   2. Create a mount point on alice, 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_alice

   5. Unmount the disk on alice:

      root # umount /srv/r0

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

      root # drbdadm secondary

2. Test the DRBD service on bob.

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

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

      root # drbdadm primary

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

      root # rcdrbd status

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

      root # mkdir /srv/r0mount

   5. On bob, mount the DRBD device:

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

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

      root # ls /srv/r0

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

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

4. Set up alice as the primary again.

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

      root # umount /srv/r0

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

      root # drbdadm secondary

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

      root # drbdadm primary

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

      rcdrbd status

5. 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 OpenAIS. For information about installing and configuring OpenAIS for SUSE Linux Enterprise 11 see Part II, “Configuration and Administration”.