How to Set Up DRBD and Keepalived for Real‑Time File Sync and Failover

Install DRBD and keepalived for Real‑Time File Synchronization and Dual‑Node Failover

System Initialization

Ensure a data disk or additional partition is available. yum update -y Disable the firewall:

systemctl stop firewalld
systemctl disable firewalld

Edit /etc/hosts to add the two nodes:

192.168.1.240 Primary kylin-01
192.168.1.241 Secondary kylin-02

Disable SELinux:

vim /etc/sysconfig/selinux
# set SELINUX=disabled

Install required packages:

yum install gcc libxslt-devel libxslt perl keyutils-libs-devel net-tools -y

Download and Compile DRBD

Download and build the DRBD kernel module:

wget https://pkg.linbit.com//downloads/drbd/9/drbd-9.2.8.tar.gz
tar -zxvf drbd-9.2.8.tar.gz
cd drbd-9.2.8
make && make install

Download and install drbd‑utils:

wget https://pkg.linbit.com//downloads/drbd/utils/drbd-utils-9.27.0.tar.gz
tar -zxvf drbd-utils-9.27.0.tar.gz
cd drbd-utils-9.27.0
./configure --prefix=/usr/local/drbd --without-83support --with-udev --with-initscripttype=systemd --without-manual
make && make install

Installed binaries are located in /usr/sbin/drbdsetup, /usr/sbin/drbdmeta, and /usr/sbin/drbdadm. Configuration files reside in /usr/local/drbd/etc/drbd.d.

Configure DRBD

Create a global configuration file global_common.conf (example content omitted for brevity).

Create a resource definition /usr/local/drbd/etc/drbd.d/drbd.res on both nodes:

resource r1 {
    protocol C;
    on kylin-01 {
        device /dev/drbd0;
        disk /dev/sdb1;
        address 192.168.1.240:7789;
        meta-disk internal;
    }
    on kylin-02 {
        device /dev/drbd0;
        disk /dev/sdb1;
        address 192.168.1.241:7789;
        meta-disk internal;
    }
}

Initialize and Start DRBD

# Create metadata
drbdadm create-md r1

# Start the service on both nodes
systemctl start drbd
systemctl enable drbd

# Verify the service is listening
netstat -anp | grep 7789

Check the role of each node with drbdadm role r1. The first node will be Secondary by default.

Promote a node to primary:

drbdadm primary --force r1
drbdadm status r1

After synchronization, the status will show role:Primary and disk:UpToDate.

Test DRBD Synchronization

Format the DRBD device and mount it on the primary node:

mkfs.ext4 /dev/drbd0
mkdir /data
mount /dev/drbd0 /data

Create a test file, unmount, switch roles, and verify the file appears on the secondary node after it becomes primary.

Handling Common Issues

If umount reports “device is busy”, find the holding process with fuser -m /data and kill it.

In a split‑brain scenario, follow the official DRBD manual to discard one side’s data and reconnect:

# On the secondary node
 drbdadm secondary r1
 drbdadm disconnect all
 drbdadm --discard-my-data connect r1

# On the primary node
 drbdadm disconnect all
 drbdadm connect r1
 drbdsetup /dev/drbd0 primary

Install and Configure keepalived

Install keepalived via yum: yum install -y keepalived Configure a virtual IP (e.g., 192.168.1.239) and set authentication. The master node’s notify_master script promotes DRBD to primary, mounts the filesystem, and starts the PostgreSQL container. The backup node’s notify_backup and notify_stop scripts stop the container, unmount the filesystem, and demote DRBD.

Enable and start keepalived on both nodes:

systemctl enable keepalived
systemctl start keepalived

Verify failover by creating or deleting data in the PostgreSQL container, then switching the virtual IP between nodes; the data should remain synchronized via DRBD.