[DRBD-user] Minor number count for DRBD 8.4

Matthias Hensler lists-drbd at wspse.de
Thu May 22 14:13:58 CEST 2014

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Thu, May 22, 2014 at 01:14:51PM +0200, Bram Klein Gunnewiek wrote:
> >On Thu, May 22, 2014 at 12:24:58PM +0200, Lars Ellenberg wrote:
> >>On Thu, May 15, 2014 at 01:17:33PM +0200, Bram Klein Gunnewiek wrote:
> >>>We are upgrading our internal tools to support DRBD 8.4. When using
> >>>8.3 we had a specific DRBD configuration in /etc/modprobe.d that set
> >>>the minor_count to 128 e.g.:
> >>>root at testnode1:~# cat /etc/modprobe.d/drbd.conf
> >>>options drbd usermode_helper=/root/true minor_count=128
> >>See also:
> >>http://www.gossamer-threads.com/lists/drbd/users/26150#26150
> >>
> >>Recommendation: leave it at its default.
> >Thanks for the clarification. However, for me one point is still
> >unanswered: how to use more than 255 DRBDs (which should be possible
> >according to the documentation).
> >
> >I posted some details in this threads:
> >http://www.gossamer-threads.com/lists/drbd/users/26000#26000
> >
> >Would be nice if you could clarify that too, thanks.
> Working with minor numbers > 255 works without a problem for me?
> As a test I set-up a new drbd resource using minor number 256 like this:

Thanks for your answer, I will redirect it to the mailing, hope that is

> # Underlaying logical volumes
> lvcreate -n test -L 1GiB vg1
> lvcreate -n test_meta -L 128M vg1
> # Resource + Minor
> drbdsetup new-resource test
> drbdsetup new-minor test /dev/drbd256 0
> # Init drbd meta
> drbdmeta --force /dev/drbd0 v08 /dev/vg1/test_meta 0 create-md
> drbdmeta --force /dev/drbd0 v08 /dev/vg1/test_meta 0 apply-al
> # Attach
> drbdsetup attach /dev/drbd256 /dev/vg1/test /dev/vg1/test_meta 0
> This works. cat /proc/drbd shows this:
> root at testnode1:~# cat /proc/drbd
> version: 8.4.3 (api:1/proto:86-101)
> srcversion: F97798065516C94BE0F27DC
> 256: cs:StandAlone ro:Secondary/Unknown ds:Inconsistent/DUnknown r-----
>     ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048320
> root at testnode1:~#
> I use drbd8-utils version 2:8.4.4-1ubuntu1.

That indeed works (using the lowlevel-tools directly). Doing the same
with drbdadm however fails with:

The highest minor you have in your config is 256but a minor_count of 128
in your config!

The solution is just to remove the definition of "minor_count" from the
config completly (previously I only tried a higher value, but that did
not work).

So it might be a good idea to mention this in the documentation (in the
section upgrading from 8.3). Maybe the drbdtools should also issue a
deprecation warning whenever minor_count is used in the configuration.

To sum fix up: make sure to remove minor_count from the configuration in
DRBD 8.4, and everything is fine.


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