What Are the Features of DRBD?

DRBD stands for Distributed Replicated Block Device. It is an open-source solution that provides a high-availability and efficient distributed storage system for cluster environments. It replicates data between systems so that applications running on the hosts see it as a single, reliable storage system.

With DRBD, block devices like hard drives, partitions, or logical volumes can be mirrored to create high-availability clusters.

Key Features of DRBD

1. Secure Authentication

   Supports shared-secret authentication to ensure secure communication between nodes.

2. LVM (Logical Volume Manager) Compatibility

   Works seamlessly with LVM for flexible disk management.

3. Integration with Resource Management Tools

   Compatible with tools like Heartbeat and Pacemaker for managing high-availability resources.

4. Load Balancing

   Distributes read requests across nodes for better performance.

Components of DRBD

1. drbd:

   The kernel module that handles the core replication process.

2. drbdadm:

   A command-line tool for managing DRBD configurations. It reads the configuration file and manages tasks.

3. drbdsetup:

   Configures the DRBD kernel module. Typically, you don't need to run this directly.

4. drbdmeta:

   Manages metadata structures for DRBD. Direct usage is rare.

How to Install and Configure DRBD

Here’s how you can set up DRBD on two nodes running Ubuntu 14.04 LTS Server.

Setup Overview

• Two nodes: drbd-server1 and drbd-server2

• Two network interfaces:

  • eth0: Used for external access via HA tools.

  • eth1: Dedicated for DRBD replication.

• IP addresses:

  • 10.0.6.200 for drbd-server1

  • 10.0.6.201 for drbd-server2

Step-by-Step Configuration

Step 1: Configure Network

On drbd-server1, edit /etc/network/interfaces to add:

 
auto eth1
iface eth1 inet static
address 10.0.6.200
netmask 255.255.255.0
network 10.0.6.0
broadcast 10.0.6.255 
                                    

Step 2: Update /etc/hosts

Add these entries on both nodes:

 
10.0.6.200 drbd-server1  
10.0.6.201 drbd-server2 
                                    

Then reboot both servers.

Step 3: Install DRBD

Run this command on both nodes:

 
sudo apt-get install drbd8-utils 
                                    

Step 4: Verify Configuration Files

Check /etc/drbd.conf for these lines:

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

Step 5: Configure global_common.conf

Edit /etc/drbd.d/global_common.conf on both nodes:

 
global {  
  usage-count yes;  
}  
common {  
  net {  
    protocol C;  
  }  
} 
                                    

Step 6: Create the Resource File

Edit /etc/drbd.d/r0.res on both nodes:

 
resource r0 {  
  device /dev/drbd1;  
  disk /dev/sdb1;  
  meta-disk /dev/sda2;  
  on drbd-server1 {  
    address 10.0.6.200:7789;  
  }  
  on drbd-server2 {  
    address 10.0.6.201:7789;  
  }  
} 
                                    

Step 7: Clear Metadata on /dev/sda2

Run this command to avoid conflicts:

 
sudo dd if=/dev/zero of=/dev/sda2 
                                    

Step 8: Create Metadata for DRBD

Run:

 
sudo drbdadm create-md r0 
                                    

Step 9: Enable the Resource

Activate the resource:

 
sudo drbdadm up r0 
                                    

Step 10: Check DRBD Status

Verify the DRBD status:

 
cat /proc/drbd 
                                    

Step 11: Start Synchronization

Make drbd-server1 the primary node:

 
sudo drbdadm primary --force r0 
                                    

Check the synchronization process using:

 
cat /proc/drbd 
                                    

Conclusion

DRBD (Distributed Replicated Block Device) offers a robust solution for high-availability and efficient distributed storage. With features like secure authentication, LVM compatibility, integration with resource management tools, and load balancing, DRBD ensures that your data is reliably replicated across nodes, providing a seamless storage experience for cluster environments. By following the detailed steps provided for installation and configuration, you can set up DRBD on your servers, ensuring data redundancy and high availability for your applications