My notes of a quick drdb test...
The Distributed Replicated Block Device (DRBD) provides a networked version of data mirroring, classified under the redundant array of independent disks (RAID) taxonomy as RAID-1.
Showing status, add a file and check target…
After initial sync:
```
**Create filesystem and some data:**
[root@drdb01 ~]# drbdadm status test test role:Primary disk:UpToDate peer role:Secondary replication:Established peer-disk:UpToDate [root@drdb02 ~]# drbdadm status test test role:Secondary disk:UpToDate peer role:Primary replication:Established peer-disk:UpToDate ```
```
**Switch roles and check SECONDARY:**
[root@drdb01 ~]# mkfs -t ext4 /dev/drbd0 [root@drdb01 ~]# mkdir -p /mnt/DRDB_PRI [root@drdb01 ~]# mount /dev/drbd0 /mnt/DRDB_PRI [root@drdb01 ~]# cd /mnt/DRDB_PRI [root@drdb01 DRDB_PRI]# ls -l total 16 drwx------. 2 root root 16384 Aug 6 10:12 lost+found [root@drdb01 DRDB_PRI]# yum install wget [root@drdb01 DRDB_PRI]# wget https://osdn.net/projects/systemrescuecd/storage/releases/6.0.3/systemrescuecd-6.0.3.iso 2019-08-06 10:18:13 (4.61 MB/s) - ‘systemrescuecd-6.0.3.iso’ saved [881852416/881852416] [root@drdb01 DRDB_PRI]# ls -lh total 842M drwx------. 2 root root 16K Aug 6 10:12 lost+found -rw-r--r--. 1 root root 841M Apr 14 08:52 systemrescuecd-6.0.3.iso ```
```
**Switch roles back:**
[root@drdb01 ~]# umount /mnt/DRDB_PRI [root@drdb01 ~]# drbdadm secondary test [root@drdb02 ~]# drbdadm primary test [root@drdb02 ~]# mkdir -p /mnt/DRDB_SEC [root@drdb02 ~]# mount /dev/drbd0 /mnt/DRDB_SEC [root@drdb02 ~]# cd /mnt/DRDB_SEC [root@drdb02 DRDB_SEC]# ls -lh total 842M drwx------. 2 root root 16K Aug 6 10:12 lost+found -rw-r--r--. 1 root root 841M Apr 14 08:52 systemrescuecd-6.0.3.iso ```
```
Detailed steps below of how we got to above test…
**Node 1 Setup and start initial sync:**
[root@drdb02 DRDB_SEC]# cd [root@drdb02 ~]# umount /mnt/DRDB_SEC [root@drdb02 ~]# drbdadm secondary test [root@drdb01 ~]# drbdadm primary test [root@drdb01 ~]# mount /dev/drbd0 /mnt/DRDB_PRI ```
```
**Node 2 setup and start initial sync:**
rrosso ~ ssh root@192.168.1.95 [root@drdb01 ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org [root@drdb01 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm [root@drdb01 ~]# yum install -y kmod-drbd84 drbd84-utils [root@drdb01 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.1.96" port port="7789" protocol="tcp" accept' success [root@drdb01 ~]# firewall-cmd --reload success [root@drdb01 ~]# yum install policycoreutils-python [root@drdb01 ~]# semanage permissive -a drbd_t [root@drdb01 ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/cl-root 6.2G 1.2G 5.1G 20% / devtmpfs 990M 0 990M 0% /dev tmpfs 1001M 0 1001M 0% /dev/shm tmpfs 1001M 8.4M 992M 1% /run tmpfs 1001M 0 1001M 0% /sys/fs/cgroup /dev/sda1 1014M 151M 864M 15% /boot tmpfs 201M 0 201M 0% /run/user/0 [root@drdb01 ~]# init 0 rrosso ~ 255 ssh root@192.168.1.95 [root@drdb01 ~]# fdisk -l | grep sd Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors /dev/sda1 * 2048 2099199 1048576 83 Linux /dev/sda2 2099200 16777215 7339008 8e Linux LVM Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors [root@drdb01 ~]# vi /etc/drbd.d/global_common.conf [root@drdb01 ~]# vi /etc/drbd.d/test.res [root@drdb01 ~]# uname -n drdb01.localdomain ** partition disk [root@drdb01 ~]# fdisk /dev/sdb [root@drdb01 ~]# vi /etc/drbd.d/test.res [root@drdb01 ~]# drbdadm create-md test initializing activity log initializing bitmap (640 KB) to all zero Writing meta data... New drbd meta data block successfully created. [root@drdb01 ~]# drbdadm up test The server's response is: you are the 18305th user to install this version [root@drdb01 ~]# vi /etc/drbd.d/test.res [root@drdb01 ~]# drbdadm down test [root@drdb01 ~]# drbdadm up test [root@drdb01 ~]# drbdadm status test test role:Secondary disk:Inconsistent peer role:Secondary replication:Established peer-disk:Inconsistent [root@drdb01 ~]# drbdadm primary --force test [root@drdb01 ~]# drbdadm status test test role:Primary disk:UpToDate peer role:Secondary replication:SyncSource peer-disk:Inconsistent done:0.01 [root@drdb01 ~]# drbdadm status test test role:Primary disk:UpToDate peer role:Secondary replication:SyncSource peer-disk:Inconsistent done:3.80 [root@drdb01 ~]# drbdadm status test test role:Primary disk:UpToDate peer role:Secondary replication:SyncSource peer-disk:Inconsistent done:85.14 ```
```
**LINKS:**
https://www.linbit.com/en/disaster-recovery/
https://www.tecmint.com/setup-drbd-storage-replication-on-centos-7/
rrosso ~ ssh root@192.168.1.96 [root@drdb01 ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org [root@drdb01 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm [root@drdb01 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.1.95" port port="7789" protocol="tcp" accept' success [root@drdb01 ~]# firewall-cmd --reload success [root@drdb01 ~]# yum install policycoreutils-python [root@drdb01 ~]# semanage permissive -a drbd_t [root@drdb01 ~]# init 0 rrosso ~ 255 ssh root@192.168.1.96 root@192.168.1.96's password: Last login: Tue Aug 6 09:46:34 2019 [root@drdb01 ~]# fdisk -l | grep sd Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors /dev/sda1 * 2048 2099199 1048576 83 Linux /dev/sda2 2099200 16777215 7339008 8e Linux LVM Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors [root@drdb01 ~]# vi /etc/drbd.d/global_common.conf [root@drdb01 ~]# vi /etc/drbd.d/test.res ** partition disk [root@drdb01 ~]# fdisk /dev/sdb [root@drdb01 ~]# fdisk -l | grep sd Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors /dev/sda1 * 2048 2099199 1048576 83 Linux /dev/sda2 2099200 16777215 7339008 8e Linux LVM Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors /dev/sdb1 2048 41943039 20970496 83 Linux [root@drdb01 ~]# vi /etc/drbd.d/test.res [root@drdb01 ~]# drbdadm create-md test initializing activity log initializing bitmap (640 KB) to all zero Writing meta data... New drbd meta data block successfully created. ** note I had wrong hostname because I cloned 2nd VM [root@drdb01 ~]# drbdadm up test you are the 18306th user to install this version drbd.d/test.res:6: in resource test, on drdb01.localdomain: IP 192.168.1.95 not found on this host. [root@drdb01 ~]# vi /etc/drbd.d/test.res [root@drdb01 ~]# uname -a Linux drdb01.localdomain 3.10.0-957.27.2.el7.x86_64 #1 SMP Mon Jul 29 17:46:05 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux [root@drdb01 ~]# vi /etc/hostname [root@drdb01 ~]# vi /etc/hosts [root@drdb01 ~]# reboot rrosso ~ 255 ssh root@192.168.1.96 [root@drdb02 ~]# uname -a Linux drdb02.localdomain 3.10.0-957.27.2.el7.x86_64 #1 SMP Mon Jul 29 17:46:05 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux [root@drdb02 ~]# drbdadm up test [root@drdb02 ~]# drbdadm status test test role:Secondary disk:Inconsistent peer role:Secondary replication:Established peer-disk:Inconsistent [root@drdb02 ~]# drbdadm status test test role:Secondary disk:Inconsistent peer role:Primary replication:SyncTarget peer-disk:UpToDate done:0.21 [root@drdb02 ~]# drbdadm status test test role:Secondary disk:Inconsistent peer role:Primary replication:SyncTarget peer-disk:UpToDate done:82.66 ```