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yoyozhu
Contributor
Contributor

DRS rules, VMs to host (KB1005508), what if host fails?

Hello all,

We are in the process to run some Prod SQL servers in groups, and only on two separate hosts in the vCenter cluster. The idea is to save some licensing cost.

So I think VMs to host (KB1005508) can be straight forward, however, I would like to have some understanding of what if the specific host fails unexpectedly? Would the VMs go down with the host as they have to run on that host?

Thanks in advance.

2 Replies
rcporto
Leadership
Leadership

The HA behavior will depends of the type of DRS rule you create, and the following blog post explain that in details: Should or Must VM-Host affinity rules? - frankdenneman.nl

How does HA treat preferential rules?

VMware High Availability respects mandatory rules and obey mandatory rules when placing virtual machines after a host failover. It can only place virtual machines on the ESX hosts that are specified in the DRS host group. DRS does not communicate the existence of preferential rules to HA, therefore HA is not aware of these rules. HA cannot prevent placing the virtual machine on a ESX host that is not a part of the DRS host group, thereby violating the affinity rule. DRS will correct this violation during the next invocation.

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Richardson Porto
Senior Infrastructure Specialist
LinkedIn: http://linkedin.com/in/richardsonporto
yoyozhu
Contributor
Contributor

Hi Richardson,

Thanks for the link, very good reading.

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