<font size=2 face="Arial">hi,</font>
<br>
<br>
<br>
<br>
<br><font size=1 color=#5f5f5f face="sans-serif">Von:
</font><font size=1 face="sans-serif">Dejan Muhamedagic <dejanmm@fastmail.fm></font>
<br><font size=1 color=#5f5f5f face="sans-serif">An:
</font><font size=1 face="sans-serif">The Pacemaker cluster
resource manager <pacemaker@oss.clusterlabs.org></font>
<br><font size=1 color=#5f5f5f face="sans-serif">Datum:
</font><font size=1 face="sans-serif">28.10.2014 16:45</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Betreff:
</font><font size=1 face="sans-serif">Re: [Pacemaker]
fencing with multiple node cluster</font>
<br>
<hr noshade>
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<br><tt><font size=2>></font></tt>
<br><tt><font size=2>>Hi,<br>
><br>
>On Tue, Oct 28, 2014 at 09:51:02AM -0400, Digimer wrote:<br>
>>> On 28/10/14 05:59 AM, philipp.achmueller@arz.at wrote:<br>
>>> hi,<br>
>>><br>
>>> any recommendation/documentation for a reliable fencing implementation<br>
>>> on a multi-node cluster (4 or 6 nodes on 2 site).<br>
>>> i think of implementing multiple node-fencing devices for
each host to<br>
>>> stonith remaining nodes on other site?<br>
>>><br>
>>> thank you!<br>
>>> Philipp<br>
>><br>
>> Multi-site clustering is very hard to do well because of fencing
issues. <br>
>> How do you distinguish a site failure from severed links?<br>
><br>
>Indeed. There's a booth server managing the tickets in<br>
>pacemaker, which uses arbitrators to resolve ties. booth source<br>
>is available at github.com and packaged for several<br>
>distributions at OBS<br>
>(</font></tt><a href="http://download.opensuse.org/repositories/network:/ha-clustering:/Stable/"><tt><font size=2>http://download.opensuse.org/repositories/network:/ha-clustering:/Stable/</font></tt></a><tt><font size=2>)<br>
>It's also supported in the newly released SLE12.<br>
><br>
>Thanks,<br>
><br>
>Dejan</font></tt>
<br><tt><font size=2>></font></tt>
<br><tt><font size=2>hi,</font></tt>
<br>
<br><tt><font size=2>@Digimer. thank you for explaination, but manual failover
between sites isn't what i'm looking for.</font></tt>
<br>
<br><tt><font size=2>@Dejan. Yes, i already tried a cluster(SLES11SP3)
with booth setup. i used documentation from sleha11 SP3. </font></tt>
<br><tt><font size=2>but i'm afraid it is unclear for me how "fencing"
with booth exactly works in case of some failures (loss-policy=fence).
documentation says something like: ...to speed up recovery process nodes
get fenced... do i need classic node-fencing(IPMI) when i configure booth
setup? may you have some more information about that?</font></tt>
<br>
<br><tt><font size=2>For correct setup, the arbitrator needs an adequate
3th location. site A and site B need separate connection to site C, otherwise
some scenarios will fail.</font></tt>
<br><tt><font size=2>any possibilities to get this running with 2 sites?</font></tt>
<br>
<br><tt><font size=2>thank you!<br>
</font></tt>
<br><tt><font size=2><br>
>> Given that a <br>
>> failed fence action can not be assumed to be a success, then the
only <br>
>> safe option is to block until a human intervenes. This makes your
<br>
>> cluster as reliable as your WAN between the sites, which is too
say, not <br>
>> very reliable. In any case, the destruction of a site will require
<br>
>> manual failover, which can be complicated if insufficient nodes
remain <br>
>> to form quorum.<br>
>><br>
>> Generally, I'd recommend to different clusters, one per site,
with <br>
>> manual/service-level failover in the case of a disaster.<br>
>><br>
>> In any case; A good fencing setup should have two fence methods.
<br>
>> Personally, I always use IPMI as a primary fence method (routed
through <br>
>> one switch) and a pair of switched PDUs as backup (via a backup
switch). <br>
>> This way, when IPMI is available, a confirmed fence is 100% certain
to <br>
>> be good. However, if the node is totally disabled/destroyed, IPMI
will <br>
>> be lost and the cluster will switch to the switched PDUs, cutting
the <br>
>> power outlets feeding the node.<br>
>><br>
>> I've got a block diagram of how I do this:<br>
>><br>
>> </font></tt><a href=https://alteeve.ca/w/AN!Cluster_Tutorial_2#A_Map.21><tt><font size=2>https://alteeve.ca/w/AN!Cluster_Tutorial_2#A_Map.21</font></tt></a><tt><font size=2><br>
>><br>
>> It's trivial to scale the idea up to multiple node clusters.<br>
>><br>
>> Cheers<br>
>><br>
>> -- <br>
>> Digimer<br>
>> Papers and Projects: </font></tt><a href=https://alteeve.ca/w/><tt><font size=2>https://alteeve.ca/w/</font></tt></a><tt><font size=2><br>
>> What if the cure for cancer is trapped in the mind of a person
without <br>
>> access to education?<br>
>><br>
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>><br>
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