JohnsVCP5
Enthusiast
Enthusiast

Admission control Policy

Hi All,

We have two hosts in cluster having sufficient resource 5 VMs but Admission control Policy is disabled on this cluster

Do we need to enable the Admission control Policy?

Thanks for advance

Regards,

Johnson.s

4 Replies
jhague
VMware Employee
VMware Employee

You need to enable admission control if you want to guarantee sufficient resources exist to power up VMs in the event of a host failure. E.g. You would set to 50% if you wanted to ensure there are sufficient resources held back to accommodate a host failure and continue running your VMs without contention.

John Hague http://linkedin.com/in/john-hague | twitter @jhague10 VCIX-DCV | VCP-DCV 3/4/5/6 | VCP6-NV | VCP7-CMA | VCAP7-CMA Design
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Nick_Andreev
Expert
Expert

Admission Control is mostly a useless feature as it guarantees resource availability only if you use CPU/memory reservations on all of your VMs. Which no one does. So I'd suggest to just keep it disabled.

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jhague
VMware Employee
VMware Employee

Not necessarily, if you use VM Resource Reduction Event Threshold then actual utilisation will be taken into account or if you use a dedicated failover hosts then reservations aren't really relevant. I'm not sure there's much to be gained by disabling it but you're right that you need to think through the consequences of what you want/expect to happen in a failover scenario.

John Hague http://linkedin.com/in/john-hague | twitter @jhague10 VCIX-DCV | VCP-DCV 3/4/5/6 | VCP6-NV | VCP7-CMA | VCAP7-CMA Design
Nick_Andreev
Expert
Expert

I stand corrected. "Performance degradation VMs tolerate" is indeed useful. It's just a warning, but it's based on real resource utilisation and not reservations. Which one step forward.

Speaking of "Dedicated failover hosts". It's also somewhat useful, but because it dedicates a host for failover and not let VMs run on it, it's almost never used.

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If you found my answers helpful please consider marking them as helpful or correct.
VCIX-DCV, VCIX-NV, VCAP-CMA | vExpert '16, '17, '18
Blog: http://niktips.wordpress.com | Twitter: @nick_andreev_au
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