Riaan's SysAdmin Blog

My tips, howtos, gotchas, snippets and stuff. Use at your own risk!

drdb

POC of drdb replication

admin

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:

[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

Create filesystem and some data:

[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 and check SECONDARY:

[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

Switch roles back:

[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

Detailed steps below of how we got to above test…

Node 1 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

Node 2 setup and start initial sync:

 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

LINKS:

https://www.linbit.com/en/disaster-recovery/
https://www.tecmint.com/setup-drbd-storage-replication-on-centos-7/

admin

Bio Info for Riaan