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

[Lars Ellenberg]

On Tue, Jul 23, 2019 at 11:51:50AM -0400, Paul Clements wrote:
> > One thing you could check just to be sure is whether the configuration
> > files are identical on all three systems.
> 
> Yes, it's identical. md5sums check out.
> 
> > Was DRBD stopped on all three nodes before you recreated the meta data?
> > (Did you do 'drbdsetup down resourcename' on all three nodes, then
> > recreate the meta data on all three nodes, and then try 'drbdadm up
> > resourcename'?)
> 
> I did:
> 
> # drbdadm down r0
> 
> Before I did the rest of those steps, yes.

> > With that information I may be able to recreate the situation if the
> > problem persists.
> 
> Thanks for the help.
> 
> The conf file is at bottom for reference. Does anyone have a working
> three node drbd.conf they'd be willing to post? I'm starting to think
> something in my conf file is odd.

Config file looks okay on first glance.
Though usually people don't directly refer to /dev/dm-X,
but to the "logical name" (devicemapper minors are not stable).

So I'd expected a /dev/mapper/vg-lv or /dev/vg/lv to be used
instead of /dev/dm-0.

Can you post a "transscript"?

Volume group scratch, LV name s0:
VG=scratch
LV=s0
size_gb=75

lvcreate -n $LV -L ${size_gb} $VG
# zero out first and last megabyte;
# if you prefer, just leave off -o and -l, to zero-out all of it.
blkdiscard -v -z -o 0 -l 1M /dev/$VG/$LV
blkdiscard -v -z -o $(( ${size_gb} * 2**30 - 2**20 )) -l 1M /dev/$VG/$LV

Make your config file refer to disk /dev/$VG/$LV

dmesg -c > /dev/null	# clear dmesg before the test
drbdadm -v create-md	# on all nodes
drbdadm -v up all	# on all nodes
dmesg			# if it failed
drbdsetup status -vvs
drbdsetup show
*now* do the mkfs on drbd, once, on one node.


-- 
: Lars Ellenberg
: LINBIT | Keeping the Digital World Running
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