[ClusterLabs] SBD with shared block storage (and watchdog?)

Klaus Wenninger kwenning at redhat.com
Mon Feb 13 18:18:52 EST 2017 

On 02/13/2017 07:34 PM, durwin at mgtsciences.com wrote:
> emmanuel segura <emi2fast at gmail.com> wrote on 02/13/2017 10:55:58 AM:
>
> > From: emmanuel segura <emi2fast at gmail.com>
> > To: Cluster Labs - All topics related to open-source clustering
> > welcomed <users at clusterlabs.org>
> > Date: 02/13/2017 10:56 AM
> > Subject: Re: [ClusterLabs] SBD with shared block storage (and
> watchdog?)
> >
> > modprobe softdog if you don't have an external watchdog
>
> Thank you, that made sbd watch happy.

But be aware that softdog won't reboot your system once kernel-facilities
needed by it (e.g. timers, switching between threads and alike) are hung.
There must be some kind of 'real' watchdog that just needs the hypervisor
to be working properly.

>
>
> I now have this running on the 2 nodes.
>
> 11:10 AM root at node1 ~
> fc25> ps aux|grep sbd
> root     24426  0.0  0.6  97888 13848 pts/0    SL   11:00   0:00 sbd:
> inquisitor
> root     24427  0.0  0.6  97892 13988 pts/0    SL   11:00   0:00 sbd:
> watcher: /dev/sdb1 - slot: 0 - uuid: 6094f0f4-2a07-47db-b4f7-6d478464d56a
> root     24428  0.0  0.8 102476 18404 pts/0    SL   11:00   0:00 sbd:
> watcher: Pacemaker
> root     29442  0.0  0.0 118520  1000 pts/0    S+   11:18   0:00 grep
> --color=auto sbd
>
> 11:18 AM root at node2 ~
> fc25> ps aux|grep sbd
> root     22784  0.0  0.6  97884 13844 pts/0    SL   11:18   0:00 sbd:
> inquisitor
> root     22785  0.0  0.6  97888 13984 pts/0    SL   11:18   0:00 sbd:
> watcher: /dev/sdb1 - slot: 1 - uuid: 6094f0f4-2a07-47db-b4f7-6d478464d56a
> root     22786  0.0  0.8 102472 18400 pts/0    SL   11:18   0:00 sbd:
> watcher: Pacemaker
> root     22789  0.0  0.0 118520   952 pts/0    S+   11:18   0:00 grep
> --color=auto sbd
>
> Is the fencing complete?
> If so, will 'pcs cluster standby' simulate node failure?

Looks as if you don't have a fencing-agent configured.
So pacemaker won't be able to actually fence a peer.
I'm using fence_sbd as RHC-style fence-agent.

Once you have that you can use stonith_admin to list
the fencing-devices and test-fence a node.

>
> Addressing email that has followed.
>
> The device sbd1 is solely for sbd.  Sounds like you're saying it does
> not get mounted.
> Is that correct?  If I just unmount sbd1 will all be ok?
> How small can I make the sbd block device?

If you don't mount it that should be OK. But you probably should create
the slots once
again to be on the safe side because the mounted filesystem might have
overwritten
something.
You can make the partition pretty small as one of these slots doesn't
need too much
space (would have to check in the sources to be sure - think the manpage
doesn't say
it) and you don't have to initialize 255 slots.

>
>
> Thank you,
>
> Durwin
>
>
> >
> > 2017-02-13 18:34 GMT+01:00  <durwin at mgtsciences.com>:
> > > I am working to get an active/active cluster running.
> > > I have Windows 10 running 2 Fedora 25 Virtualbox VMs.
> > > VMs named node1, and node2.
> > >
> > > I created a vdi disk and set it to shared.
> > > I formatted it to gfs2 with this command.
> > >
> > > mkfs.gfs2 -t msicluster:msigfs2 -j 2 /dev/sdb1
> > >
> > > After installing 'dlm' and insuring guest additions were
> > > installed, I was able to mount the gfs2 parition.
> > >
> > > I then followed.
> > >
> > > https://github.com/l-mb/sbd/blob/master/man/sbd.8.pod
> > >
> > > I used this command.
> > >
> > > sbd -d /dev/sdb1 create
> > >
> > > Using sbd to 'list' returns nothing, but 'dump' shows this.
> > >
> > > fc25> sbd -d /dev/sdb1 dump
> > > ==Dumping header on disk /dev/sdb1
> > > Header version     : 2.1
> > > UUID               : 6094f0f4-2a07-47db-b4f7-6d478464d56a
> > > Number of slots    : 255
> > > Sector size        : 512
> > > Timeout (watchdog) : 5
> > > Timeout (allocate) : 2
> > > Timeout (loop)     : 1
> > > Timeout (msgwait)  : 10
> > > ==Header on disk /dev/sdb1 is dumped
> > >
> > > I then tried the 'watch' command and journalctl shows error listed.
> > >
> > > sbd -d /dev/sdb1 -W -P watch
> > >
> > > Feb 13 09:54:09 node1 sbd[6908]:    error: watchdog_init: Cannot open
> > > watchdog device '/dev/watchdog': No such file or directory (2)
> > > Feb 13 09:54:09 node1 sbd[6908]:  warning: cleanup_servant_by_pid:
> Servant
> > > for pcmk (pid: 6910) has terminated
> > > Feb 13 09:54:09 node1 sbd[6908]:  warning: cleanup_servant_by_pid:
> Servant
> > > for /dev/sdb1 (pid: 6909) has terminated
> > >
> > >
> > > From
> > >
> > > http://blog.clusterlabs.org/blog/2015/sbd-fun-and-profit
> > >
> > > I installed watchdog.
> > >
> > > my /etc/sysconfig/sbd is.
> > >
> > > SBD_DELAY_START=no
> > > SBD_OPTS=
> > > SBD_PACEMAKER=yes
> > > SBD_STARTMODE=clean
> > > SBD_WATCHDOG_DEV=/dev/watchdog
> > > SBD_WATCHDOG_TIMEOUT=5
> > >
> > > the sbd-fun-and-profit says to use this command.
> > >
> > > virsh edit vmnode
> > >
> > > But there is no vmnode and no instructions on how to create it.
> > >
> > > Is anyone able to piece together the missing steps?
> > >
> > >
> > > Thank you.
> > >
> > > Durwin F. De La Rue
> > > Management Sciences, Inc.
> > > 6022 Constitution Ave. NE
> > > Albuquerque, NM  87110
> > > Phone (505) 255-8611
> > >
> > >
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