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HA and DRS balance

Posted on 2015-02-02
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Last Modified: 2015-03-06
Have a cluster and both DRS and HA re enabled.
I forced one esxi host to enter into maintenance mode and noticed all the vm were migrated to other esxi host.
I rebooted the the esxi host after applying the patches.
I was expecting few vms to come back to this esxi host to balance the cluster, but it did not happen.
My assumption was that resources in the cluster will be balanced and vm will be motioned to balance the cluster if there is a requirement?
Does not it happen automatically, does it need manual intervention?
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Question by:sara2000
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by:asavener
asavener earned 143 total points
ID: 40584623
Depends on the DRS settings.  DRS can be configured to be manual or automatic, and the automatic settings can be configured.  Right-click the cluster, select Edit Settings, and then click on "VMware DRS."

Check your settings, and how aggressive the migration threshold is.  

If it is set to "manual" and you want to move some machines, you can left-click the cluster, select the DRS tab, and then select "Run DRS."  It will then give recommendations which you can choose to apply.

(If DRS is set to Automatic, then selecting "Run DRS" may result in machines being automatically vMotioned to other hosts.)
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by:asavener
ID: 40584635
And HA is for automatically restarting VMs when the host fails, so it will not get activated when a host gracefully enters maintenance mode.
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by:Andrew Hancock (VMware vExpert / EE MVE)
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ID: 40584642
Give it a while, and eventually it will move VMs. (based on the number of VMs, and how heavy they are using resources!)

BUT DRS is not loading balancing, so do not expect it to be 50% CPU on Host A, 50 % CPU on Host B, and 50% Memory on Host A ot 50 % Memory on Hots B.

Also do you have it set to FULLY Automatic ?
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by:gheist
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DRS is polled every 5 minutes. You can force it with "RUN DRS" button in cluster DRS panel
Unless you set DRS to highest level no migrations will happen unless some host is under resource pressure.
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by:sara2000
ID: 40585017
DRS is on  automatic. Strange one esxi host is always complaining (alerts) about host memory .
I did "RUN DRS" nothing happened? should it move VMs out of this esxi if this esxi  has memory issue?
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by:gheist
ID: 40585025
Can you post authentic host memory complaint?
And a probe in vcenter alerts that triggers it?
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by:asavener
ID: 40585109
Are you clearing the alert, and then it alerts again?  The alert icon will continue to be displayed until the alarm is cleared.
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gheist earned 144 total points
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Would be nice to know it it is hardware alert or overcommit alert.....
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by:sara2000
ID: 40606611
Gheist:
How do i find whether it is hardware alert or overcommit alert?
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by:Andrew Hancock (VMware vExpert / EE MVE)
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Alerts Tab, at the root of your vCenter Server.

It will still be there, unless you've cleared it.

The alert will be triggered also on the host, a Red Alert on the host.

see here....

Alerts
The is a HA and DRS Cluster, and quite simply, there is *NOT* enough Memory in the hosts!

DRS and HA will not prevent this, they just move VMs around hosts!

You will still get memory warning's and cpu, if you do not have enough resources.

Time to either add more memory to ALL your hosts, or reduce the memory in use by your VMs if possible. But if it's all active, time to update your memory in all your hosts!
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by:asavener
asavener earned 143 total points
ID: 40606722
Try selecting the host, and then going to the "hardware status" tab.  You should see any hardware errors there.

ESXi will inspect the BIOS log to see if there were any POST errors logged.  If it sees any (even if the errors have been resolved), it will generate an alert.  To make sure the error doesn't recur, you have to reboot, go into the BIOS, and clear the log.


That's if there's a hardware issue.
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by:sara2000
ID: 40606791
I see very often on one esxi host as on Adrew's screen shot , not on all esxi hosts in the cluster.
I do clear that alert from time to time then it come back.
I was expecting a vm/vms should be moved out of that particular esxi to free out memory in both HA and DRS are enabled. It does not happen my case.
I am wondering why that esxi host get memory alert but vms are not moving ?
Does this means that other esxi hosts do not have enough memory to accept the vm?
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by:gheist
ID: 40606795
CAN YOU LOOK AT HARDWARE STATUS
Or you think we will poke around for another month?
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by:Andrew Hancock (VMware vExpert / EE MVE)
Andrew Hancock (VMware vExpert / EE MVE) earned 213 total points
ID: 40606820
It's also happening, in in that screenshot. HA and DRS are enabled, a host is down, Hosts are alerting with memory issues, because both are at 95%-100%, and DRS has no where to more the VM - so what do we do....

Yes, it means you've ran out of resources, like I have in that cluster, because a machine has failed!

Add more resources, either another server, with CPU and Memory, or add more CPU or Memory to hosts.

What do you think the problem is here:- ?

Alerts1
and DRS is not moving my VMs, why?

and is this what you are observing, if you are clearing events, what action are you taking, if you just keep clearing them.......
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