Re: [OSR-devel] OSR on DRBD+GFS

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On Saturday 09 February 2008 19:30:48 Gordan Bobic wrote:
> Marc Grimme wrote:
> > Hi Gordan,
> >
> > On Saturday 09 February 2008 01:56:18 Gordan Bobic wrote:
> >> Hi,
> >>
> >> I'm trying to add support for DRBDs, and trying to stick with doing it
> >> in a way consistent with iSCSI support as far as it is possible. I'm
> >> seeing a few weird things, though.
> >>
> >> In linuxrc.generic.sh:
> >> [...]
> >> # start iscsi if apropriate
> >> isISCSIRootsource $rootsource
> >> if [ $? -eq 0 ]; then
> >>          loadISCSI
> >>          startISCSI $rootsource $nodename
> >> fi
> >>
> >> # start drbd if appropriate
> >> isDRBDRootSource $rootsource
> >> if [ $? -eq 0 ]; then
> >>          loadDRBD
> >>          startDRBD $rootsource $nodename
> >> fi
> >> [...]
> >>
> >> and in cluster.conf:
> >> [...]
> >> <clusternodes>
> >>                  <clusternode name="sentinel1c" nodeid="1" votes="2">
> >>                          <com_info>
> >>                                  <rootsource name="drbd"/>
> >>
> >> [...]
> >
> > Agreed. That's the place.You also have a bootoption rootsource to
> > overwrite it. Normally we would suspect rootsource to be some kind of url
> > like for example iscsi://iscsi-host/export-name or it might be
> > drbd://slave/export or something. I cannot remember the semantics there
> > too long ago ;-) .
> >
> > Are you also aware of the com-expert bootoption? This one is quite handy
> > as it brings you to a shell before the process of the initrd is started.
> > And you can change some things to see if they work or not.
> >
> > Answer to the iscsi questioning stuff.
> > [marc@mobilix-07 boot-scripts]$ source etc/iscsi-lib.sh
> > [marc@mobilix-07 boot-scripts]$ isISCSIRootsource drbd
> > [marc@mobilix-07 boot-scripts]$ echo $?
> > 1
> > [marc@mobilix-07 boot-scripts]$ isISCSIRootsource iscsi
> > [marc@mobilix-07 boot-scripts]$ echo $?
> > 0
> > [marc@mobilix-07 boot-scripts]$
> >
> > So if we are going iscsi we'll return a '0'. As a successfully executed
> > shellscript does.
> >
> >>  From this, one would assume that isISCSIRootsource would return false
> >> and iSCSI not get initialized, and isDRBDRootSource would return true
> >> and get initialized.
> >>
> >> This is the opposite of what I'm seeing. iSCSI gets started, and the
> >> modules loaded. DRBD doesn't.
> >>
> >> Am I misunderstanding where $nodename is coming from? I'm not
> >> particularly bothered by iSCSI trying to start (and failing because the
> >> iscsi packages aren't in the rpm list), but that makes the drbd not
> >> starting all the more puzzling. :-/
> >
> > $nodename is the nodename that belongs to the node in bootprocess. But it
> > is not necessarily the hostname. The function
> > cluster-lib.sh/getClusterFSParameters returns it. It's a little bit
> > calling other functions to make it more independent from the cluster.conf
> > (that was the idea in the first place).
>
> Ah, I see. I think it may be necessary to do
> hostname $nodename
> in that case, since DRBD requires hostname to be matching the node name
> in the DRBD configuration.
Hmm. That would be a way.
>
> >> Further on (unrelated to this), I get cman starting, but ccsd failing,
> >> so the boot-up aborts. But ps -aux | grep ccsd shows that ccsd is in
> >> fact already running. I haven't seen this behaviour before. The only
> >> thing I can think of that is different is that this is a 2-node cluster,
> >> which is much smaller than what I usually work with. (Yes I did set
> >> <cman two_node="1" expected_votes="2"/>)
> >
> > Enable syslogging to a syslog server. <syslog name="server"/> does the
> > trick and see what it tells you.
>
> I'm feeling a bit silly now. The answer was in the line I pasted. For
> two_node=1, expected_votes needs to be 1 as well. :-/
>
> On a separate note, is there a configurable way to disable LVM/CLVM,
> even if only at mkinitrd time? All it is achieving for me is throwing up
> ugly "FAILED" startup messages because I'm not using LVM. I could
> comment it out of the boot scripts, but that seems a bit nasty.
Ok so what we did the last time was to introduce the lvm_check (Wasn't it 
because of your request?! ;-) ) function in linux.generic.rc line 288. That 
function checks for your rootdevice (specified in the cluster.conf) for it 
being a lv or not (seeing if it exists and if it has lvm major/minors).
Doesn't that functionality work?

It would also be possible to add a nolvm as we recently added a nousb 
bootoption. How about that as an addition?

Recipe: 
Add a new option to boot-lib/getBootParameters at the end of the function:
----------------------------------
echo -n ":"
getBootParm nolvm
----------------------------------
Then add to linux.generic.sh below the nousb line114:
-----------------------------------------------------------------
nolvm=$(getParm ${bootparms} 8)
-----------------------------------------------------------------
and then instead of linux.generic.rc line 290:
------------------------------------------------------------------
if [ "$lvm_sup" -eq 0 ] || [ -z "$nolvm" ]; then
-------------------------------------------------------------------
There you go. I think that'll do it.
>
> I'm about 99% there with getting a single node to boot of the
> OSR/GFS/DRBD. I just need to write a quick wrapper and it'll be ready.
> Hoping to post a patch tomorrow.
Sounds very great. We'll appreciate it very much.
>
> Gordan
Marc.
>
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-- 
Gruss / Regards,

Marc Grimme
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