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<div>Cern actually did a pretty good write up of this:</div>
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<div>http://openstack-in-production.blogspot.com/2014/07/openstack-plays-tetris-stacking-and.html</div>
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<div><font class="Apple-style-span" color="#000000"><font class="Apple-style-span" face="Calibri"><span class="Apple-style-span" style="font-size: 14px;">Kris Lindgren</span></font></font></div>
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<span style="font-weight:bold">From: </span>Adam Lawson <<a href="mailto:alawson@aqorn.com">alawson@aqorn.com</a>><br>
<span style="font-weight:bold">Date: </span>Thursday, March 3, 2016 at 4:28 PM<br>
<span style="font-weight:bold">To: </span>Silence Dogood <<a href="mailto:matt@nycresistor.com">matt@nycresistor.com</a>><br>
<span style="font-weight:bold">Cc: </span>"<a href="mailto:openstack-operators@lists.openstack.org">openstack-operators@lists.openstack.org</a>" <<a href="mailto:openstack-operators@lists.openstack.org">openstack-operators@lists.openstack.org</a>><br>
<span style="font-weight:bold">Subject: </span>Re: [Openstack-operators] Setting affinity based on instance type<br>
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<div dir="ltr">Mathieu,
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<div>Blame it on my scattered brain but I'm now curious. How would this be approached practically speaking? I.e. how would
<font face="monospace,monospace">ram_weight_multiplier</font> enable the scenario I mentioned in my earliest post ?</div>
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<div>//adam</div>
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Adam Lawson</i></b></div>
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<div class="gmail_quote">On Thu, Mar 3, 2016 at 10:43 AM, Silence Dogood <span dir="ltr">
<<a href="mailto:matt@nycresistor.com" target="_blank">matt@nycresistor.com</a>></span> wrote:<br>
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<div dir="ltr">cool!</div>
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<div class="gmail_quote">On Thu, Mar 3, 2016 at 1:39 PM, Mathieu Gagné <span dir="ltr">
<<a href="mailto:mgagne@internap.com" target="_blank">mgagne@internap.com</a>></span> wrote:<br>
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<span>On 2016-03-03 12:50 PM, Silence Dogood wrote:<br>
> We did some early affinity work and discovered some interesting problems<br>
> with affinity and scheduling. =/ by default openstack used to ( may<br>
> still ) deploy nodes across hosts evenly.<br>
><br>
> Personally, I think this is a bad approach. Most cloud providers stack<br>
> across a couple racks at a time filling them then moving to the next.<br>
> This allows older equipment to age out instances more easily for removal<br>
> / replacement.<br>
><br>
> The problem then is, if you have super large capacity instances they can<br>
> never be deployed once you've got enough tiny instances deployed across<br>
> the environment. So now you are fighting with the scheduler to ensure<br>
> you have deployment targets for specific instance types ( not very<br>
> elastic / ephemeral ). goes back to the wave scheduling model being<br>
> superior.<br>
><br>
> Anyways we had the braindead idea of locking whole physical nodes out<br>
> from the scheduler for a super ( full node ) instance type. And I<br>
> suppose you could do this with AZs or regions if you really needed to.<br>
> But, it's not a great approach.<br>
><br>
> I would say that you almost need a wave style scheduler to do this sort<br>
> of affinity work.<br>
><br>
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</span>You can already do it with the RAMWeigher using the<br>
ram_weight_multiplier config:<br>
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Multiplier used for weighing ram. Negative<br>
numbers mean to stack vs spread.<br>
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Default is 1.0 which means spread.<br>
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--<br>
Mathieu<br>
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