Tuesday, November 25, 2025

DRBD : Install

 

DRBD : Install

 

Install DRBD (Distributed Replicated Block Device) to configure Distributed Storage System.
This example is based on the environment like follows.

+----------------------+          |          +----------------------+
| [   DRBD Server#1  ] |10.0.0.51 | 10.0.0.52| [   DRBD Server#2  ] |
|   node01.srv.world   +----------+----------+   node02.srv.world   |
|                      |                     |                      |
+----------------------+                     +----------------------+

It needs that the server you'd like to install DRBD has free block-device.

[1]Install and Configure DRBD on all Nodes.
root@node01:~# 
apt -y install drbd-utils
root@node01:~# 
vi /etc/drbd.d/r0.res
# create new : file name ⇒ (resource name).res

resource r0 {
    net {
    	# A : write completion is determined when data is written to the local disk and the local TCP transmission buffer
        # B : write completion is determined when data is written to the local disk and remote buffer cache
        # C : write completion is determined when data is written to both the local disk and the remote disk
        protocol C;
        cram-hmac-alg sha1;
        # any secret key for authentication among nodes
        shared-secret "MySharedSecret";
    }
    disk {
    	# possible to limit bandwidth for sync (example is 10MB/sec)
        resync-rate 10M;
    }
    # on (hostname)
    on node01.srv.world {
    address 10.0.0.51:7788;
        volume 0 {
            # device name
            device /dev/drbd0;
            # specify disk to be used for devide above
            disk /dev/sdb1;
            # where to create metadata
            # specify the block device name when using a different disk
            meta-disk internal;
        }
    }
    on node02.srv.world {
        address 10.0.0.52:7788;
        volume 0 {
            device /dev/drbd0;
            disk /dev/sdb1;
            meta-disk internal;
        }
    }
}

# load module

root@node01:~# 
modprobe drbd

root@node01:~# 
lsmod | grep drbd

drbd                  487424  0
lru_cache              16384  1 drbd
libcrc32c              12288  1 drbd

# create DRBD resource

root@node01:~# 
drbdadm create-md r0

initializing activity log
initializing bitmap (2560 KB) to all zero
Writing meta data...
New drbd meta data block successfully created.

root@node01:~# 
systemctl enable --now drbd

[2]After configuring on all Nodes, Sync data on a Node.
# current status is [Secondary/Secondary]

root@node01:~# 
cat /proc/drbd

version: 8.4.11 (api:1/proto:86-101)
srcversion: 900745622289D38C0BAB129
 0: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r-----
    ns:0 nr:0 dw:0 dr:0 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:83882460

# UP DRBD resource

root@node01:~# 
drbdadm up r0
# get primary role and sync data

root@node01:~# 
drbdadm -- --overwrite-data-of-peer primary r0
# data sync starts

root@node01:~# 
cat /proc/drbd

version: 8.4.11 (api:1/proto:86-101)
srcversion: 900745622289D38C0BAB129
 0: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
    ns:4216536 nr:0 dw:0 dr:4216536 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:79665924
        [>...................] sync'ed:  5.1% (77796/81916)M
        finish: 0:35:43 speed: 37,152 (34,004) K/sec

# when the sync is complete, the status will be as follows

root@node01:~# 
cat /proc/drbd

version: 8.4.11 (api:1/proto:86-101)
srcversion: 900745622289D38C0BAB129
 0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
    ns:83882460 nr:0 dw:0 dr:83882460 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0
[3]That's OK. After that, you can use it by creating a file system on the DRBD device and mounting it on the primary side.
root@node01:~# 
mkfs.ext4 /dev/drbd0

root@node01:~# 
mkdir /drbd_disk

root@node01:~# 
mount /dev/drbd0 /drbd_disk

root@node01:~# 
df -hT

Filesystem                  Type      Size  Used Avail Use% Mounted on
udev                        devtmpfs  1.9G     0  1.9G   0% /dev
tmpfs                       tmpfs     392M  560K  392M   1% /run
/dev/mapper/debian--vg-root ext4       27G  955M   25G   4% /
tmpfs                       tmpfs     2.0G     0  2.0G   0% /dev/shm
tmpfs                       tmpfs     5.0M     0  5.0M   0% /run/lock
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
tmpfs                       tmpfs     2.0G     0  2.0G   0% /tmp
/dev/vda1                   ext4      943M   74M  804M   9% /boot
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/getty@tty1.service
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/serial-getty@ttyS0.service
tmpfs                       tmpfs     392M  4.0K  392M   1% /run/user/0
/dev/drbd0                  ext4       79G  2.1M   75G   1% /drbd_disk

# create a test file

root@node01:~# 
echo 'test file' > /drbd_disk/test.txt

root@node01:~# 
ll /drbd_disk

total 20
drwx------ 2 root root 16384 Aug 20 12:25 lost+found
-rw-r--r-- 1 root root    10 Aug 20 12:26 test.txt
[4]To mount DRBD device on the secondary Host, do it like follows.
# on primary host
# unmount drbd device and set secondary

root@node01:~# 
umount /drbd_disk

root@node01:~# 
drbdadm secondary r0
# on secondary host
# set primary and mount drbd device

root@node02:~# 
drbdadm primary r0

root@node02:~# 
mount /dev/drbd0 /drbd_disk

root@node02:~# 
df -hT

Filesystem                  Type      Size  Used Avail Use% Mounted on
udev                        devtmpfs  1.9G     0  1.9G   0% /dev
tmpfs                       tmpfs     392M  560K  392M   1% /run
/dev/mapper/debian--vg-root ext4       27G  955M   25G   4% /
tmpfs                       tmpfs     2.0G     0  2.0G   0% /dev/shm
tmpfs                       tmpfs     5.0M     0  5.0M   0% /run/lock
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
tmpfs                       tmpfs     2.0G     0  2.0G   0% /tmp
/dev/vda1                   ext4      943M   74M  804M   9% /boot
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/getty@tty1.service
tmpfs                       tmpfs     1.0M     0  1.0M   0% /run/credentials/serial-getty@ttyS0.service
tmpfs                       tmpfs     392M  4.0K  392M   1% /run/user/0
/dev/drbd0                  ext4       79G  2.1M   75G   1% /drbd_disk

root@node02:~# 
cat /drbd_disk/test.txt

test file

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