No. When a node is lost, fenced is called. Fenced informs DLM that a
fence is pending and DLM stops issuing locks. Only after fenced confirms
successful fence is DLM told. The DLM will reap locks held by the
now-fenced node and recovery can begin.
Anything using DLM; rgmanager, clvmd, gfs2, will block. This is by
design. If you ever allowed a cluster to make an assumption about the
state of a lost node, you risk a split-brain. If a split-brain was
tolerable, you wouldn't need an HA cluster. :)
digimer
On 01/02/14 04:11 PM, nik600 wrote:
Ok but is not possible to ignore fence?
Il 01/feb/2014 22:09 "Digimer" <lists@xxxxxxxxxx
<mailto:lists@xxxxxxxxxx>> ha scritto:
Ooooh, I'm not sure what option you have then. I suppose
fence_virtd/fence_xvm is your best option, but you're going to need
to have the admin configure the fence_virtd side.
On 01/02/14 03:50 PM, nik600 wrote:
My problem is that i don't have root access at host level.
Il 01/feb/2014 19:49 "Digimer" <lists@xxxxxxxxxx
<mailto:lists@xxxxxxxxxx>
<mailto:lists@xxxxxxxxxx <mailto:lists@xxxxxxxxxx>>> ha scritto:
On 01/02/14 01:35 PM, nik600 wrote:
Dear all
i need some clarification about clustering with rhel 6.4
i have a cluster with 2 node in active/passive
configuration, i
simply
want to have a virtual ip and migrate it between 2 nodes.
i've noticed that if i reboot or manually shut down a
node the
failover
works correctly, but if i power-off one node the
cluster doesn't
failover on the other node.
Another stange situation is that if power off all the
nodes and then
switch on only one the cluster doesn't start on the
active node.
I've read manual and documentation at
https://access.redhat.com/____site/documentation/en-US/Red_____Hat_Enterprise_Linux/6/html/____Cluster_Administration/index.____html
<https://access.redhat.com/__site/documentation/en-US/Red___Hat_Enterprise_Linux/6/html/__Cluster_Administration/index.__html>
<https://access.redhat.com/__site/documentation/en-US/Red___Hat_Enterprise_Linux/6/html/__Cluster_Administration/index.__html
<https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Cluster_Administration/index.html>>
and i've understand that the problem is related to
fencing, but the
problem is that my 2 nodes are on 2 virtual machine , i
can't
control
hardware and can't issue any custom command on the
host-side.
I've tried to use fence_xvm but i'm not sure about it
because if
my VM
has powered-off, how can it reply to fence_vxm messags?
Here my logs when i power off the VM:
==> /var/log/cluster/fenced.log <==
Feb 01 18:50:22 fenced fencing node mynode02
Feb 01 18:50:53 fenced fence mynode02 dev 0.0 agent
fence_xvm
result:
error from agent
Feb 01 18:50:53 fenced fence mynode02 failed
I've tried to force the manual fence with:
fence_ack_manual mynode02
and in this case the failover works properly.
The point is: as i'm not using any shared filesystem
but i'm only
sharing apache with a virtual ip, i won't have any
split-brain
scenario
so i don't need fencing, or not?
So, is there the possibility to have a simple "dummy"
fencing?
here is my config.xml:
<?xml version="1.0"?>
<cluster config_version="20" name="hacluster">
<fence_daemon clean_start="0" post_fail_delay="0"
post_join_delay="0"/>
<cman expected_votes="1" two_node="1"/>
<clusternodes>
<clusternode name="mynode01"
nodeid="1" votes="1">
<fence>
<method name="mynode01">
<device
domain="mynode01"
name="mynode01"/>
</method>
</fence>
</clusternode>
<clusternode name="mynode02"
nodeid="2" votes="1">
<fence>
<method name="mynode02">
<device
domain="mynode02"
name="mynode02"/>
</method>
</fence>
</clusternode>
</clusternodes>
<fencedevices>
<fencedevice agent="fence_xvm"
name="mynode01"/>
<fencedevice agent="fence_xvm"
name="mynode02"/>
</fencedevices>
<rm log_level="7">
<failoverdomains>
<failoverdomain name="MYSERVICE"
nofailback="0"
ordered="0" restricted="0">
<failoverdomainnode
name="mynode01"
priority="1"/>
<failoverdomainnode
name="mynode02"
priority="2"/>
</failoverdomain>
</failoverdomains>
<resources/>
<service autostart="1" exclusive="0"
name="MYSERVICE"
recovery="relocate">
<ip address="192.168.1.239"
monitor_link="on"
sleeptime="2"/>
<apache config_file="conf/httpd.conf" name="apache"
server_root="/etc/httpd" shutdown_wait="0"/>
</service>
</rm>
</cluster>
Thanks to all in advance.
The fence_virtd/fence_xvm agent works by using multicast to
talk to
the VM host. So the "off" confirmation comes from the
hypervisor,
not the target.
Depending on your setup, you might find better luck with
fence_virsh
(I have to use this as there is a known multicast issue
with Fedora
hosts). Can you try, as a test if nothing else, if
'fence_virsh'
will work for you?
fence_virsh -a <host ip> -l root -p <host root pw> -n
<virsh name
for target vm> -o status
If this works, it should be trivial to add to cluster.conf.
If that
works, then you have a working fence method. However, I would
recommend switching back to fence_xvm if you can. The
fence_virsh
agent is dependent on libvirtd running, which some consider
a risk.
hth
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