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<div class="moz-cite-prefix">On 18/09/15 07:30, Luca Bertoncello
wrote:<br>
</div>
<blockquote
cite="mid:DC8168E813106D47ADB2BA2C8A46E9FF327AB9C13C@sphinx.queo.local"
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi
all,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">thank you very much for your answers.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">So:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><span style="mso-list:Ignore">1)<span
style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">Of course, we have UPS. More than one, in our
server room, and of course they will send an advice to the
host if they are on battery</span></p>
</div>
</blockquote>
<br>
Good.<br>
<br>
<blockquote
cite="mid:DC8168E813106D47ADB2BA2C8A46E9FF327AB9C13C@sphinx.queo.local"
type="cite">
<div class="WordSection1">
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><span style="mso-list:Ignore">2)<span
style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">My question was: “what can I do, so that in
case of Kernel Panic or similar, the VM will be migrated
(live or not) to another host?”</span></p>
</div>
</blockquote>
<br>
You would make the VMs HA and acquire a fencing solution.<br>
<br>
<blockquote
cite="mid:DC8168E813106D47ADB2BA2C8A46E9FF327AB9C13C@sphinx.queo.local"
type="cite">
<div class="WordSection1">
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><span style="mso-list:Ignore">3)<span
style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">I’d like to have a shutdown-script on the host
that put the host in Maintenance and wait until it’s done,
so that I can just shutdown or reboot it without any other
action. Is it possible? It would help to manage the power
failure, too, assuming that other hosts have better UPS (it
can be possible…)</span></p>
</div>
</blockquote>
<br>
You could probably use the REST API on the Ovirt Engine for that.But
it might be better to have a highly available machine (VM or not)
running something like Nagios or Icinga which would perform the
monitoring of your hosts and connect to the REST API to perform
maintenance and shutdown. You might also consider a UPS service like
NUT (unless you're already doing it).<br>
<br>
Cheers<br>
<br>
Alex<br>
<br>
<blockquote
cite="mid:DC8168E813106D47ADB2BA2C8A46E9FF327AB9C13C@sphinx.queo.local"
type="cite">
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lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">Thanks a lot<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Mit
freundlichen Grüßen<br>
<br>
Luca Bertoncello<br>
<br>
-- <br>
Besuchen Sie unsere Webauftritte:<o:p></o:p></span></p>
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<p class="MsoNormal"><span
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Luca Bertoncello<br>
Administrator<o:p></o:p></span></p>
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<p class="MsoNormal"><span
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queo GmbH<br>
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<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
<a class="moz-txt-link-abbreviated" href="mailto:users-bounces@ovirt.org">users-bounces@ovirt.org</a>
[<a class="moz-txt-link-freetext" href="mailto:users-bounces@ovirt.org">mailto:users-bounces@ovirt.org</a>] <b>On Behalf Of </b>matthew
lagoe<br>
<b>Sent:</b> Thursday, September 17, 2015 9:56 PM<br>
<b>To:</b> 'Alex Crow'; 'Yaniv Kaul'<br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:users@ovirt.org">users@ovirt.org</a><br>
<b>Subject:</b> Re: [ovirt-users] Automatically
migrate VM between hosts in the same cluster<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US">There are PDU’s that you can monitor power
draw per port and that would kind of tell you if a PSU
failed as the load would be 0<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:users-bounces@ovirt.org">users-bounces@ovirt.org</a>
[<a moz-do-not-send="true"
href="mailto:users-bounces@ovirt.org">mailto:users-bounces@ovirt.org</a>]
<b>On Behalf Of </b>Alex Crow<br>
<b>Sent:</b> Thursday, September 17, 2015 12:31 PM<br>
<b>To:</b> Yaniv Kaul <<a moz-do-not-send="true"
href="mailto:ykaul@redhat.com">ykaul@redhat.com</a>><br>
<b>Cc:</b> <a moz-do-not-send="true"
href="mailto:users@ovirt.org">users@ovirt.org</a><br>
<b>Subject:</b> Re: [ovirt-users] Automatically
migrate VM between hosts in the same cluster<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
lang="EN-US">I don't really think this is practical:<br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">- If the PSU
failed, your UPS could alert you. If you have
one...<o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
lang="EN-US"><br>
If you have only one PSU in a host, a UPS is not going to
stop you losing all the VMs on that host. OK, if you had
N+1 PSUs, you may be able to monitor for this
(IPMI/LOM/DRAC etc)and use the API to put a host into
maintenance. Also a lot of people rely on low-cost
white-box servers and decide that it's OK if a single PSU
in a host dies, as, well, we have HA to start on other
hosts. If they have N+1 PSUs in the hosts do they really
have to migrate everything off? Swings and roundabouts
really.<br>
<br>
I'm also not sure I've seen any practical DC setups where
a UPS can monitor the load for every single attached
physical machine and figure out that one of the redundant
PSUs in it has failed - I'd love to know if there are as
that would be really cool.<br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">- If the
machine is going down in an ordinary flow,
surely it can be done. <o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
lang="EN-US"><br>
Isn't that what "Maintenance mode" is for?<br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">Â <o:p></o:p></span></p>
</div>
<blockquote style="border:none;border-left:solid
#CCCCCC 1.0pt;padding:0cm 0cm 0cm
6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
<p class="MsoNormal"><span lang="EN-US"><br>
Even if it was a network failure and the host
was still up, how would you live migrate a VM
from a host you can't even talk to?<o:p></o:p></span></p>
</blockquote>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">It could be
suspended to disk (local) - if the disk is
available.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Then the
decision if it is to be resumed from local disk
or not (as it might be HA'ed and is running
elsewhere) need to be taken later, of course.<o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
lang="EN-US"><br>
Yes, but that's not even remotely possible with Ovirt
right now. I was trying to be practical as the OP has only
just started using Ovirt and I think it might be a bit
much to ask him to start coding up what he'd like.<br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Â <o:p></o:p></span></p>
</div>
<blockquote style="border:none;border-left:solid
#CCCCCC 1.0pt;padding:0cm 0cm 0cm
6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
<p class="MsoNormal"><span lang="EN-US"><br>
The only way you could do it was if you somehow
magically knew far enough in advance that the
host was about to fail (!) and that gave enough
time to migrate the machines off. But how would
you ever know that "machine <a
moz-do-not-send="true"
href="http://quux.bar.net" target="_blank">quux.bar.net</a>
is going to fail in 7 minutes"?<o:p></o:p></span></p>
</blockquote>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">I completely
agree there are situations in which you can't
foresee the failure. <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">But in many,
you can. In those cases, it makes sense for the
host to self-initiate 'move to maintenance'
mode. The policy of what to do when
'self-moving-to-maintenance-mode' could be
pre-fetched from the engine.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Y.<o:p></o:p></span></p>
</div>
</div>
</div>
</div>
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<p class="MsoNormal"><span lang="EN-US"><br>
Hmm, I would love that to be true. But I've seen so many
so called "corner-cases" that I now think the failure area
in a datacenter is a fractal with infinite corners. Yes,
you could monitor SMART on local drives, pick up
uncorrected ECC errors, use "sensors" to check for sagging
voltages or high temps, but I don't think you can ever
hope to catch everything, and you could end up doing a
migration "storm" for . I've had more than enough of
"Enterprise Spec" switches suddenly going nuts and
spamming corrupt MACs all over the LAN to know you can't
ever account for everything.<br>
<br>
I think it's better to adopt the model of redundancy in
software and services, so no-one even notices if a VM host
goes away, there's always something else to take up the
slack. Just like the origins of the Internet - the network
should be dumb and the applications should cope with it!
Any infrastructure that can't cope with the loss of a few
VMs for a few minutes probably needs a refresh.<br>
<br>
Cheers<br>
<br>
Alex<br>
<br>
<br>
<br>
<br>
<br>
. <o:p></o:p></span></p>
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