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<div class="moz-cite-prefix">Explained here also:<br>
<br>
<a class="moz-txt-link-freetext" href="http://clusterlabs.org/doc/crm_fencing.html">http://clusterlabs.org/doc/crm_fencing.html</a><br>
<br>
<div class="paragraph">
<p><small><i>The lights-out devices (IBM RSA, HP iLO, Dell DRAC)
are becoming
increasingly popular and in future they may even become
standard
equipment of of-the-shelf computers. They are, however,
inferior
to UPS devices, because they share a power supply with
their host
(a cluster node). If a node stays without power, the
device
supposed to control it would be just as useless. Even
though this
is obvious to us, the cluster manager is not in the know
and will
try to fence the node in vain. This will continue forever
because
all other resource operations would wait for the
fencing/stonith
operation to succeed.</i></small></p>
</div>
<br>
Regards.<br>
<br>
El 04/03/15 a las 09:28, Jose Manuel Martínez escribió:<br>
</div>
<blockquote cite="mid:54F6C215.6030906@fcsc.es" type="cite">
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<div class="moz-cite-prefix">I understand the problem. <br>
<br>
Fencing and reallocation of resources is not possible if the
fencing resource is not able to know the real status of the
other node. So, I'm going to try to remove this single point of
failure adding a second fencing method (thanks for the links).
Our PDU's are not able to disconnect a sinble power bank, so
this is not actually an option for us, but I think we have other
options. <br>
<br>
I'll post if I can solve the problem. Thank you so much. You
have been very helpfull.<br>
<br>
JoseM<br>
<br>
<br>
El 03/03/15 a las 19:51, Digimer escribió:<br>
</div>
<blockquote cite="mid:54F602C3.5020005@alteeve.ca" type="cite">
<pre wrap="">-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 03/03/15 01:42 PM, Ken Gaillot wrote:
</pre>
<blockquote type="cite">
<pre wrap="">On 03/03/2015 01:14 PM, Jose Manuel Martínez wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hello everybody.
I'm trying to build an active/passive cluster for the Lustre
filesystem. Pacemaker is working fine in most situations except
one: If a node goes out of power in a 2-node cluster, and I am
using fence_ipmilan as fencing resource (for HP iLO2), the alive
node is not able to takeover the resources of the failed node. It
tries to check the fencing device trying to reboot it, but as the
node is dead (no power), the IPMI interface does not answer.
</pre>
</blockquote>
<pre wrap="">Correct, IPMI that shares power with its host should not be used as
the sole fencing device for this very reason. There is no way for
the cluster to be certain that the host is down and not just the
IPMI.
IPMI is fine as the first-attempt fencing device, but there should
be a fallback fencing device that is independent of the host (such
as a remotely controllable power switch).
</pre>
</blockquote>
<pre wrap="">I agree 100%, and do this myself.
IPMI fencing, when it works, is best because when it returns "off", we
can be *very* sure the node is actually off. As you said though, it is
electrically and mechanically coupled to the host, so it's vulnerable
to certain failure cases (ie: total loss of power, mechanical
destruction, etc).
For this, I always use a pair of switched PDUs (APC and Raritan both
work well, TrippLite works but is slow). I use a pair because I also
have power redundancy (separate UPSes, PDUs, etc). So to hand this,
you need a fairly complex stonith configuration to make it work.
In 'pcs', this is called 'STONITH Levels' and you can see how how to
build this here:
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://clusterlabs.org/wiki/STONITH_Levels">http://clusterlabs.org/wiki/STONITH_Levels</a>
In 'crm', this is called "Fencing Topology" and you can see how to
configure it here:
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://clusterlabs.org/wiki/Fencing_topology">http://clusterlabs.org/wiki/Fencing_topology</a>
In my opinion, this is the only proper configuration for fencing if
you want to remove all single points of failure.
- --
Digimer
Papers and Projects: <a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://alteeve.ca/w/">https://alteeve.ca/w/</a>
What if the cure for cancer is trapped in the mind of a person without
access to education?
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<p class="MsoNormal"><b><span
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<p class="MsoNormal"><span
style="font-size:8.0pt;font-family:"Arial","sans-serif";color:#7F7F7F">Universidad
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<p class="MsoNormal"><span
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<p class="MsoNormal"><span
style="font-size:8.0pt;font-family:"Arial","sans-serif";color:#7F7F7F">Universidad
de León<o:p></o:p></span></p>
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