POC of drdb replication

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:

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[root@drdb01 ~]# drbdadm status test
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test role:Primary
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  disk:UpToDate
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  peer role:Secondary
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    replication:Established peer-disk:UpToDate
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[root@drdb02 ~]# drbdadm status test
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test role:Secondary
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  disk:UpToDate
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  peer role:Primary
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    replication:Established peer-disk:UpToDate

Create filesystem and some data:

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[root@drdb01 ~]# mkfs -t ext4 /dev/drbd0
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[root@drdb01 ~]# mkdir -p /mnt/DRDB_PRI
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[root@drdb01 ~]# mount /dev/drbd0 /mnt/DRDB_PRI
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[root@drdb01 ~]# cd /mnt/DRDB_PRI
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[root@drdb01 DRDB_PRI]# ls -l
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total 16
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drwx------. 2 root root 16384 Aug  6 10:12 lost+found
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[root@drdb01 DRDB_PRI]# yum install wget
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[root@drdb01 DRDB_PRI]# wget https://osdn.net/projects/systemrescuecd/storage/releases/6.0.3/systemrescuecd-6.0.3.iso
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2019-08-06 10:18:13 (4.61 MB/s) - "systemrescuecd-6.0.3.iso" saved [881852416/881852416]
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[root@drdb01 DRDB_PRI]# ls -lh
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total 842M
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drwx------. 2 root root  16K Aug  6 10:12 lost+found
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-rw-r--r--. 1 root root 841M Apr 14 08:52 systemrescuecd-6.0.3.iso

Switch roles and check SECONDARY:

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[root@drdb01 ~]# umount /mnt/DRDB_PRI
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[root@drdb01 ~]# drbdadm secondary test
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[root@drdb02 ~]# drbdadm primary test
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[root@drdb02 ~]# mkdir -p /mnt/DRDB_SEC
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[root@drdb02 ~]# mount /dev/drbd0 /mnt/DRDB_SEC
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[root@drdb02 ~]# cd /mnt/DRDB_SEC
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[root@drdb02 DRDB_SEC]# ls -lh
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total 842M
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drwx------. 2 root root  16K Aug  6 10:12 lost+found
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-rw-r--r--. 1 root root 841M Apr 14 08:52 systemrescuecd-6.0.3.iso

Switch roles back:

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[root@drdb02 DRDB_SEC]# cd
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[root@drdb02 ~]# umount /mnt/DRDB_SEC
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[root@drdb02 ~]# drbdadm secondary test
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[root@drdb01 ~]# drbdadm primary test
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[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:

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rrosso  ~  ssh root@192.168.1.95
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[root@drdb01 ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
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[root@drdb01 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
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[root@drdb01 ~]# yum install -y kmod-drbd84 drbd84-utils
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[root@drdb01 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4"  source address="192.168.1.96" port port="7789" protocol="tcp" accept'
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success
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[root@drdb01 ~]# firewall-cmd --reload
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success
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[root@drdb01 ~]# yum install policycoreutils-python
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[root@drdb01 ~]# semanage permissive -a drbd_t
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[root@drdb01 ~]# df -h
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Filesystem           Size  Used Avail Use% Mounted on
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/dev/mapper/cl-root  6.2G  1.2G  5.1G  20% /
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devtmpfs             990M     0  990M   0% /dev
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tmpfs               1001M     0 1001M   0% /dev/shm
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tmpfs               1001M  8.4M  992M   1% /run
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tmpfs               1001M     0 1001M   0% /sys/fs/cgroup
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/dev/sda1           1014M  151M  864M  15% /boot
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tmpfs                201M     0  201M   0% /run/user/0
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[root@drdb01 ~]# init 0
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rrosso  ~  255  ssh root@192.168.1.95
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[root@drdb01 ~]# fdisk -l | grep sd
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Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors
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/dev/sda1   *        2048     2099199     1048576   83  Linux
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/dev/sda2         2099200    16777215     7339008   8e  Linux LVM
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Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
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[root@drdb01 ~]# vi /etc/drbd.d/global_common.conf
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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[root@drdb01 ~]# uname -n
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drdb01.localdomain
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** partition disk
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[root@drdb01 ~]# fdisk /dev/sdb
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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[root@drdb01 ~]# drbdadm create-md test
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initializing activity log
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initializing bitmap (640 KB) to all zero
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Writing meta data...
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New drbd meta data block successfully created.
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[root@drdb01 ~]# drbdadm up test
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The server's response is:
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you are the 18305th user to install this version
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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[root@drdb01 ~]# drbdadm down test
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[root@drdb01 ~]# drbdadm up test
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[root@drdb01 ~]# drbdadm status test
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test role:Secondary
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  disk:Inconsistent
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  peer role:Secondary
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    replication:Established peer-disk:Inconsistent
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[root@drdb01 ~]# drbdadm primary --force test
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[root@drdb01 ~]# drbdadm status test
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test role:Primary
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  disk:UpToDate
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  peer role:Secondary
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    replication:SyncSource peer-disk:Inconsistent done:0.01
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[root@drdb01 ~]# drbdadm status test
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test role:Primary
80
  disk:UpToDate
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  peer role:Secondary
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    replication:SyncSource peer-disk:Inconsistent done:3.80
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[root@drdb01 ~]# drbdadm status test
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test role:Primary
86
  disk:UpToDate
87
  peer role:Secondary
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    replication:SyncSource peer-disk:Inconsistent done:85.14

Node 2 setup and start initial sync:

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 rrosso  ~  ssh root@192.168.1.96
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[root@drdb01 ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
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[root@drdb01 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
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[root@drdb01 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4"  source address="192.168.1.95" port port="7789" protocol="tcp" accept'
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success
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[root@drdb01 ~]# firewall-cmd --reload
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success
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[root@drdb01 ~]# yum install policycoreutils-python
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[root@drdb01 ~]# semanage permissive -a drbd_t
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[root@drdb01 ~]# init 0
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 rrosso  ~  255  ssh root@192.168.1.96
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root@192.168.1.96's password:
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Last login: Tue Aug  6 09:46:34 2019
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[root@drdb01 ~]# fdisk -l | grep sd
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Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors
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/dev/sda1   *        2048     2099199     1048576   83  Linux
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/dev/sda2         2099200    16777215     7339008   8e  Linux LVM
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Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
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[root@drdb01 ~]# vi /etc/drbd.d/global_common.conf
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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** partition disk
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[root@drdb01 ~]# fdisk /dev/sdb
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[root@drdb01 ~]# fdisk -l | grep sd
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Disk /dev/sda: 8589 MB, 8589934592 bytes, 16777216 sectors
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/dev/sda1   *        2048     2099199     1048576   83  Linux
37
/dev/sda2         2099200    16777215     7339008   8e  Linux LVM
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Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
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/dev/sdb1            2048    41943039    20970496   83  Linux
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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[root@drdb01 ~]# drbdadm create-md test
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initializing activity log
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initializing bitmap (640 KB) to all zero
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Writing meta data...
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New drbd meta data block successfully created.
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** note I had wrong hostname because I cloned 2nd VM
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[root@drdb01 ~]# drbdadm up test
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you are the 18306th user to install this version
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drbd.d/test.res:6: in resource test, on drdb01.localdomain:
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  IP 192.168.1.95 not found on this host.
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[root@drdb01 ~]# vi /etc/drbd.d/test.res
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[root@drdb01 ~]# uname -a
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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
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[root@drdb01 ~]# vi /etc/hostname
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[root@drdb01 ~]# vi /etc/hosts
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[root@drdb01 ~]# reboot
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 rrosso  ~  255  ssh root@192.168.1.96
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[root@drdb02 ~]# uname -a
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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
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[root@drdb02 ~]# drbdadm up test
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[root@drdb02 ~]# drbdadm status test
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test role:Secondary
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  disk:Inconsistent
74
  peer role:Secondary
75
    replication:Established peer-disk:Inconsistent
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[root@drdb02 ~]# drbdadm status test
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test role:Secondary
79
  disk:Inconsistent
80
  peer role:Primary
81
    replication:SyncTarget peer-disk:UpToDate done:0.21
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[root@drdb02 ~]# drbdadm status test
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test role:Secondary
85
  disk:Inconsistent
86
  peer role:Primary
87
    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/