Saturday, September 19, 2015

How to fix Configuration issue: Unable to apply DRS resource settings on host

Last day when I was looking At my vCenter instance, found two hosts with read explanation mark on them and when checked found this configuration issue related message in summary: “Unable to apply resource settings on host. The available CPU resources in the parent resource pool are in sufficient for the operation. This can significantly reduce the effectiveness of DRS.”

Interestingly DRS is not enabled for the cluster where these hosts are located so what is the cause of this error (you may also see this kind of configuration issue message on host in a DRS enabled cluster).
When I was looking for the reason of the same, found resource reservations configured for most of the VMs in this four host cluster. I had seen this error earlier and that time was able to fix it by offloading some VMs from that host to another however this time that didn’t work and even another host started showing the same configuration issue then I tried to remove reservation but that also didn’t work.
Note: If there are enough resources available in the cluster then you may safely ignore this configuration error message. 

These are the potential fixes of above configuration error:
In order to remove this configuration error message what we can do is, first enable DRS on this cluster (if already enabled, disable it and then re-enable) and leave it for some time (if you don’t want to leave it then you may run DRS manually), if you are lucky then this would fix this the issue.

An unfinished VMware tools installation (where you initiated tools installation but it never finished) also could be a reason of this configuration issue. If that is the case, Mark that by right clicking on it => Guest => End VMware Tools Install. It will resolve the issue and the error will disappear.

If that doesn’t work then in order to fix this you will have to restart management agents on affected servers (restart the hostd and vpxa agents). After restarting the management agents this configuration issue related message will go away.

For detailed info refer to VMware KB# 10283511004667

If you have seen this configuration issue before and fixed it using any other way, please share in comment area.

That's it.... :)


2 comments:

  1. Be very careful with disabling DRS.

    When DRS is disabled, the cluster’s resource pool hierarchy and affinity rules (see Using Affinity Rules) are not reestablished when DRS is turned back on. So if you disable DRS, the resource pools are removed from the cluster. To avoid losing the resource pools, instead of disabling DRS, you should suspend it by changing the DRS automation level to manual (and disabling any virtual machine overrides). This prevents automatic DRS actions, but preserves the resource pool hierarchy.

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  2. Yes you are absolutely correct about the resource pool however disabling DRS would give you an option to take backup of resource pools but yes you would have to re-add the VMs after restoring it.

    About the DRS rules, they are actually Cluster rules however DRS should be available to take them in effect.

    Now come to the error i discussed in this post, it was there even when the DRS not enabled for the Cluster, this hosts in question is a member of.

    Thank you!

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