[DRBD-user] DRBD 9: 3-node mirror error (Low.dev. smaller than requested DRBD-dev. size.)

[Paul Clements]

RHEL 7.6 with DRBD 9.0.16

I had a two-node DRBD mirror set up, but wanted to add a third node. I
redid /etc/drbd.conf as follows:

# You can find an example in  /usr/share/doc/drbd.../drbd.conf.example

include "drbd.d/global_common.conf";
include "drbd.d/*.res";

resource r0 {
        on sios0 {
                node-id 0;
                device /dev/drbd0;
                disk /dev/dm-0;
                address 10.0.0.4:7788;
                meta-disk internal;
        }

        on sios1 {
                node-id 1;
                device /dev/drbd0;
                disk /dev/dm-0;
                address 10.0.0.7:7788;
                meta-disk internal;
        }

        on sios2 {
                node-id 2;
                device /dev/drbd0;
                disk /dev/dm-0;
                address 10.0.0.5:7788;
                meta-disk internal;
        }

        connection {
              host sios0 port 7788;
              host sios1 port 7788;
              net {
                        protocol C;
              }
        }

        connection {
              host sios0 port 7788;
              host sios2 port 7788;
              net {
                        protocol A;
              }
        }

        connection {
              host sios1 port 7788;
              host sios2 port 7788;
              net {
                        protocol A;
              }
        }
}


I zeroed out the filesystem and drbd metadata:

# dd if=/dev/zero of=/dev/dm-0 bs=1M count=128

# dd if=/dev/zero of=/dev/dm-0 bs=1M count=128 seek=71600
dd: error writing '/dev/dm-0': No space left on device

# drbdadm status
 # No currently configured DRBD found.

# drbdadm create-md r0
initializing activity log
initializing bitmap (4484 KB) to all zero
Writing meta data...
New drbd meta data block successfully created.
success

# drbdadm up r0
0: Failure: (111) Low.dev. smaller than requested DRBD-dev. size.
Command 'drbdsetup attach 0 /dev/dm-0 /dev/dm-0 internal' terminated
with exit code 10

In syslog:

Jul 19 19:19:48 sios0 kernel: drbd r0: Starting worker thread (from
drbdsetup [13041])
Jul 19 19:19:48 sios0 kernel: drbd r0 sios1: Starting sender thread
(from drbdsetup [13046])
Jul 19 19:19:48 sios0 kernel: drbd r0 sios2: Starting sender thread
(from drbdsetup [13049])
Jul 19 19:19:48 sios0 kernel: drbd r0/0 drbd0: Current (diskless)
capacity 146861616, cannot attach smaller (146857136) disk

# cat /proc/partitions | grep dm-0
 253        0   73433088 dm-0

Device is same size on all three nodes. Same error occurs on all three
nodes in "drbdadm up".

Any ideas? Something I'm doing wrong? I didn't specify a size
anywhere, so not sure why this isn't working.

Thanks,
Paul