Revision as of 16:18, 6 October 2021 by Tony (talk | contribs)

Distributed Replicated Block Device


See also: http://www.gluster.org/ and http://ceph.com/

Stacked resources










HOWTO create a drbd resource

lvcreate -L2G -n test3 DRBD

Create resource file and verify it

drbdadm dump -c test3.res

Copy the resource file to /etc/drbd.d/ on both nodes On both nodes run

drbdadm create-md test3
cat /proc/drbd


drbdadm up test3

should give:

3: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r-----

On one node run:

drbdadm -- --overwrite-data-of-peer primary test3

or just

drbdadm primary --force test3

and check:

cat /proc/drbd

which should give:

3: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
    ns:152168 nr:0 dw:0 dr:154288 al:8 bm:0 lo:0 pe:1 ua:0 ap:0 ep:1 wo:f oos:1945500
        [>...................] sync'ed:  7.5% (1945500/2097052)K

Make device/node primary

Should already be done by previous step

drbdadm primary yourdeviceID


drbdsetup /dev/drbdX primary -o

Create pcs resource

pcs resource create TEST3_DRBD ocf:linbit:drbd drbd_resource=test3 op demote interval=0s timeout=90 monitor interval=60s \
  notify interval=0s   timeout=90 promote interval=0s timeout=90 reload interval=0s timeout=30 \
  start interval=0s timeout=240 stop interval=0s timeout=100 --disabled

This will result in the error:

* TEST3_DRBD_monitor_0 on santest-b 'not configured' (6): call=922, status=complete, exitreason='meta parameter misconfigured, expected clone-max -le 2, but found unset.',
   last-rc-change='Tue Jul 21 10:06:20 2020', queued=0ms, exec=680ms

Just run

pcs resource master TEST3_DRBD-Clone TEST3_DRBD master-node-max=1 clone-max=2 notify=true   master-max=1 clone-node-max=1 --disabled

and then

pcs resource cleanup TEST3_DRBD


Grow resource

On both nodes:

lvextend -L+10G /dev/DRBD/myresource

On one node:

drbdadm resize myresource


Check resource file

Editing files in /etc/drbd.d/ is a bad plan, to check syntax first:

drbdadm dump -c /tmp/test.res


Mapping resource name and device

ls -al /dev/drbd/<LVM volume group name>/by-disk/



Renaming DRBD resource

Is a simple matter of renaming the oldresource.res file and updating its contents. Rember to first (on one node is enough):

drbdadm down myresource

and if you're like me you might need to rename your logical volume too

lvrename VG oldresource newresource

Remove drbd resource

drbdadm down myresource

remove resource files

Show statistics

drbdsetup status --verbose --statistics


Get out of 'Standalone'

disconnect/connect until works :)

1: State change failed: (-2) Need access to UpToDate data

when you get that tryinng to make a node/resource primary, try

drbdadm primary drbdX --force

Failure: (102) Local address(port) already in use.

When drbdadm shows


and or


it's already busy, check

cat /proc/drbd instead


calculate metadata size



Cs=`blockdev --getsz /dev/foo`
Bs=`blockdev --getpbsz /dev/foo`

TODO finish this

'mydrbd' not defined in your config (for this host).

If drbdadm create-md throws this, 'this host' is the clue: it must match `hostname`


show resource sizes


commands to show info



resolving split brain issues


You might try

drbdadm attach drbd0


The disk contains an unclean file system (0, 0).

Metadata kept in Windows cache, refused to mount. Falling back to read-only mount because the NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting.)

When trying to mount a snapshot (kpartx -av backup-snap1 etc)




sync is slow

On secondary:

drbdadm disk-options --c-plan-ahead=0 --resync-rate=50M drbd0

and to reset after sync:

drbdadm adjust drbd0

show configuration

drbdsetup show


show more info

drbdsetup show-gi <minor-number>

Minor number is shown in drbdsetup show

update network settings

drbdsetup net-options  --sndbuf-size=2M


mount: unknown filesystem type 'drbd'

Usually means your node is not primary. If you're sure you know what you're doing you can use

mount -t ext4 /dev/drbd1 /drbdmount

or when you want to mount the partion while drbd is down:

kpartx -av /dev/mapper/DRBD-test1 
#add map DRBD-test1p1 (253:5): 0 10482928 linear /dev/mapper/DRBD-test1 2048
#I suggest mounting ro 
mount -o ro /dev/mapper/DRBD-test1o1 /mnt/test1

reload configuration

drbdadm --dry-run adjust <resourcename|all>

and then

drbdadm adjust <resourcename|all>

show configuration of resource

drbdsetup /dev/drbd0 show


resource unknown

First try

drbdadm up resourcename

Command 'drbdmeta 1 v08 /dev/drbd0 internal apply-al' terminated with exit code 20

Most likely split brain issue, check dmesg etc


Could be split brain situation

drbdadm -- --discard-my-data connect resource

cs:StandAlone ro:Primary/Unknown ds:UpToDate/DUnknown

So you're on the primary node, secondary might showing nothing, then first

drbdadm up drbdX

or if secondary shows "cs:WFConnection ro:Secondary/Unknown ds:UpToDate/DUnknown", it is waiting for connection(no?)

drbdadm disconnect drbdres
drbdadm connect --discard-my-data drbdres

or it shows "cs:WFConnection ro:Secondary/Unknown ds:UpToDate/DUnknown", in that case what might work on primary node:

drbdadm disconnect drbdX
drbdadm connect drbdX

Split brain issue

To force updating resource

  1. You might need this
drbdadm down <resource>

This works on a device that's not shown in /proc/drbd

drbdadm invalidate <resource>

cs:WFReportParams ro:Secondary/Unknown ds:UpToDate/DUnknown

connection is made, waiting for more

cs:StandAlone ro:Secondary/Unknown ds:UpToDate/DUnknown

Assuming you really are looking at the secondary:

drbdadm -- --discard-my-data connect test3

and on primary you might need to

drbdadm connect test3


drbdadm primary --force test3


Unexpected data packet AuthChallenge (0x0010)

maybe the shared key

State change failed: Device is held open by someone

could be stacked resource, timeout?

error receiving ReportState, e: -5 l: 0!


resource XYX cannot run anwhere

If you see that in log, it probably means it's a disabled resource in a disabled group CHECK THIS

drbd: error sending genl reply

CentOS feature, https://wiki.centos.org/Manuals/ReleaseNotes/CentOS7.2003. "Try another kernel/module version"

State change failed: (-14) Need a verify algorithm to start online verify

Means no verify-alg was defined, so no online checking

drbdadm dump-md foo: Found meta data is "unclean", please apply-al first


drbdadm apply-al foo

( AL means "activity log", btw )


log messages

sock_sendmsg time expired, ko=6

latency problem?