[DRBD-user] device naming and udev + pacemaker issues

Ivan ivan at c3i.bg
Sun Sep 14 09:15:25 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.

Hello fellow drbd users

First post on the mailing list - thanks to the drbd devs and 
contributors for this great piece of software. I've been using it for 
years, it's been working flawlessly since then.

I have a production two-node pacemaker cluster (centos6) hosting a bunch 
of virtual machines and I'm doing some tests for a planned upgrade to 
centos7. With the elrepo rpm as well as the latest drbd-utils git, I get 
the following syslog error message after "drbdadm up someresourcename":

NAME="$env{DEVICE}" ignored, kernel device nodes can not be renamed; 
please fix it in /usr/lib/udev/rules.d/65-drbd.rules:8

Which effectively prevents /dev/drbd_blah from being created (eg, 
"/dev/drbd_vm-mail-data"). This is easily fixed by symlinking:

-NAME=="", ENV{DEVICE}!="", NAME="$env{DEVICE}"

(side question: I read that the by-res/ naming is 8.x legacy. Will the 
9x series drop that and use exclusively /dev/drbd[0-9]+ and 
/dev/drbd_{resourcename} devices ?)

Which leads me to a related issue with pacemaker: if I use 
/dev/drbd_blah when defining resources without fixing the udv rules, the 
drbd ocf resource file loops forever in my_udevsettle(). That's normal 
since /dev/drbd_blah  is not created, but there's no error message in 
pacemaker log files so it took me a while to figure what the problem was 
until I saw that the drbd ocf was stuck with sleep 1 processes (note to 
others: look at the output of ps axf and any processes stuck under lrmd).

Isn't it possible to have more meaningful error reporting (or a 
documented error code, but I don't see any in the OCF_ ones) ? Is it OK 
to set a timeout in the ocf filer rather than relying on pacemaker's 
defined timeout ? It would save some a lot of debugging time for the 
8x->9x transition.


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