How To Install and Configure DRBD 9（不使用LVM）

- 日理万妓 2023-10-08 08:01 33阅读 0赞

**How To Install and Configure DRBD 9 Cluster on RHEL7 / CentOS7**

written by [Lotfi Waderni][] September 22, 2017

**What is DRBD (Distributed Replicated Block Device)?**

[**DRBD** ][DRBD_](**Distributed Replicated Block Device**) is a Linux-based software component to mirror or replicate individual storage devices (such as hard disks or partitions) from one node to the other(s) over a network connection. **DRBD** makes it possible to maintain consistency of data among multiple systems in a network. **DRBD** also ensures **high availability** (HA) for Linux applications.  
**DRBD** supports three distinct replication modes, allowing three degrees of replication synchronicity.

*  Protocol A: Asynchronous replication protocol.
 *  Protocol B: Memory synchronous (semi-synchronous) replication protocol.
 *  Protocol C: Synchronous replication protocol.

In this tutorial, we are going to create and configure a **DRBD Cluster** Across two servers. Both servers have an empty disk attached /dev/sdb.

**Enviroment**

<table> 
 <tbody> 
 <tr> 
 <td> Servers </td> 
 <td> drbd1 </td> 
 <td> 192.168.111.132 </td> 
 <td> CentOS&nbsp;7 </td> 
 </tr> 
 <tr> 
 <td> drbd2 </td> 
 <td> 192.168.111.190 </td> 
 <td> CentOS&nbsp;7 </td> 
 </tr> 
 </tbody> 
</table>

**Disable SELinux on the system**

\# setenforce 0

永久关闭

可以修改配置文件/etc/selinux/config,将其中SELINUX设置为disabled。

\[root@localhost ~\]\# cat /etc/selinux/config

\# This file controls the state of SELinux on the system.

\# SELINUX= can take one of these three values:

\# enforcing - SELinux security policy is enforced.

\# permissive - SELinux prints warnings instead of enforcing.

\# disabled - No SELinux policy is loaded.

\#SELINUX=enforcing

SELINUX=disabled

\# SELINUXTYPE= can take one of three two values:

\# targeted - Targeted processes are protected,

\# minimum - Modification of targeted policy. Only selected processes are protected.

\# mls - Multi Level Security protection.

SELINUXTYPE=targeted

\# sestatus

SELinux status: disabled

**Installing DRBD**

1. In order to install **DRBD**, you will need to enable the **ELRepo repository** on both nodes, because this software package is not distributed through the standard **CentOS** and Red Hat Enterprise Linux repositories.  
Use the following commands to import **GPG key** and install **ELRepo repository** on both nodes:

\# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

\# rpm -Uvh http://www.elrepo.org/elrepo-release-**7**.0-3.el7.elrepo.noarch.rpm

2. Run the following command on both nodes to install the **DRBD** software and the all necessaries kernel modules

\# **yum** install drbd90-utils kmod-drbd90

– Once the installation is completed, you will need to check whether the kernel module is loaded correctly, using this command:

\# lsmod | grep -i **drbd**

If it is not loaded automatically, you can load the module to the kernel on both nodes, using the follow command:

\# modprobe **drbd**

Note that **modprobe** command will take care of loading the kernel module for the time being on your current session. However, in order for it to be loaded during boot, you have to make use of the **systemd-modules-load** service by creating a file inside **/etc/modulesload.d/** so that the **DRBD** module is loaded properly each time the system boots:

\# echo **drbd** > /etc/modules-load.d/**drbd**.conf

**Configuring DRBD**

After having successfully installed **DRBD** on both nodes, we need to modify the **DRBD** global and common settings by editing the file **/etc/drbd.d/global\_common.conf**.  
1. Let’s backup the original settings on both nodes with the following command:

\# mv /etc/**drbd**.d/global\_common.conf /etc/**drbd**.d/global\_common.conf.orig

2. Create a new **global\_common.conf** file on both nodes with the following contents:

\# vi /etc/**drbd**.d/global\_common.conf

global \{

usage-count no;

common \{

net \{

protocol C;

3. Next, we will need to create a new configuration file called **/etc/drbd.d/drbd0.res** for the new resource named **drbd0**, with the following  
contents:

\# vi /etc/**drbd**.d/drbd0.res

resource drbd0 \{

disk /dev/sdb;

device /dev/drbd0;

meta-disk internal;

on drbd1 \{

address 192.168.111.132:7789;

on drbd2 \{

address 192.168.111.190:7789;

In the above resource file, we created a new resource drbd0 where 192.168.111.132 and 192.168.111.190 are the IP addresses of our two nodes, and 7789 is the port used for communication, using the disk **/dev/sdb** to create the new device /dev/drbd0.

4. Initialize the meta data storage on each nodes by executing the following command on both nodes

\# drbdadm create-md drbd0

5.Starting and Enabling the **DRBD** Daemon on both nodes.

\# systemctl start **drbd**

\# systemctl enable **drbd**

6. Lets define the **DRBD** Primary node as first node “drbd1”.

\# drbdadm up drbd0

\# drbdadm primary drbd0

Note:  
if you get any error to make the node primary, use the following command to forcefully make the node as primary:

\# drbdadm primary drbd0 --force

**7**. On the Secondary node “drbd2” run the following command to start the drbd0

\# drbdadm up drbd0

8. You can check the current status of the synchronization while it’s being performed. The **cat /proc/drbd** command displays the creation and synchronization progress of the resource, as shown here:

\# cat /proc/**drbd**

**9**. Adjust the firewall using the following commands:

\# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="ip\_address" port port="7789" protocol="tcp" accept'

\# firewall-cmd --reload

**Test the DRBD**

In order to test the **DRBD** functionality we need to Create a file system, mount the volume and write some data on primary node “drbd1” and finally switch the primary node to “drbd2”

– Run the following command on the primary node to create an xfs filesystem on /dev/drbd0 and mount it to the mnt directory, using the following commands:

\# mkfs.xfs /dev/drbd0

\# mount /dev/drbd0 /mnt

– Create some data using the following command:

\# touch /mnt/file\{1..5\}

\# ls -l /mnt/

total 0

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file1

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file2

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file3

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file4

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file5

– Let’s now switch primary mode “drbd1” to second node “drbd2” to check the data replication works or not.

First, we have to unmount the volume drbd0 on the first **drbd** cluster node “drbd1”.

\# umount /mnt

Change the primary node to secondary node on the first **drbd** cluster node “drbd1”

\# drbdadm secondary **drbd0**

Change the secondary node to primary node on the second **drbd** cluster node “drbd2”

\# drbdadm primary **drbd0**

Mount the volume and check the data available or not.

\# mount /dev/drbd0 /mnt

\# ls -l /mnt

total 0

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file1

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file2

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file3

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file4

\-rw-r--r--. 1 root root 0 Sep 22 21:43 file5

We hope this tutorial was enough Helpful. If you need more information, or have any questions, just comment below and we will be glad to assist you!

Last login: Tue Oct 8 21:40:12 2019 from 192.168.111.1  
\[root@drbd1 ~\]\# drbdadm status  
drbd0 role:Secondary  
 disk:UpToDate  
drbd2 role:Primary  
peer-disk:UpToDate

\[root@drbd1 ~\]\#

\# drbdsetup status --verbose --statistics  
drbd0 node-id:1 role:Secondary suspended:no  
write-ordering:flush  
volume:0 minor:0 disk:UpToDate quorum:yes  
size:153087388 read:2120 written:0 al-writes:0 bm-writes:0 upper-pending:0  
lower-pending:0 al-suspended:no blocked:no  
drbd1 node-id:0 connection:Connected role:Secondary congested:no  
ap-in-flight:0 rs-in-flight:0  
volume:0 replication:Established peer-disk:UpToDate  
resync-suspended:no  
received:0 sent:0 out-of-sync:0 pending:0 unacked:0

[Lotfi Waderni]: http://yallalabs.com/author/admin/
[DRBD_]: https://www.linbit.com/