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From Simon Weller <>
Subject Re: System VMs not migrating when host down
Date Thu, 15 Feb 2018 16:53:20 GMT
Hey Andrija,

So it sounds like your primary storage isn't enforcing an exclusive lock.  How is your storage
exposed to ACS?

We've found that HA doesn't work at all with a host failure on KVM, as those VMs will never
be restarted until the host is either recovered, or the host is removed from ACS. We are running
a heavily patched 4.8.

- Si
From: Andrija Panic <>
Sent: Wednesday, February 14, 2018 3:22 AM
To: dev
Subject: Re: System VMs not migrating when host down

Humble opinion (until HOST HA is ready in 4.11 if not mistaken?), avoid
using HA option for VMs  - avoid setting the  "Offer HA" option on any
compute/service offerings, since we did end  up (was it ACS 4.5 or 4.8,
can't remember now) having 2 copies of SAME VM running on 2 different
hosts...imagine storage/volume corruption...this happened a few times for

HOST HA looks like really a nice thing, I have not tested that yet...but
sould completely solve the problem.

On 14 February 2018 at 10:14, Paul Angus <> wrote:

> Hi Sean,
> The 'problem' with VM HA in KVM is that it relies on the parent host agent
> to be connected to report that the VM is down.  We cannot assume that just
> because a host agent is disconnected, that the VMs on that host are not
> running.
> This is where HOST HA comes in, this feature detects loss of connection to
> the agent and then tries to determine if the VMs on that host are active
> and then attempts some corrective action.
> Kind regards,
> Paul Angus

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> -----Original Message-----
> From: Sean Lair []
> Sent: 13 February 2018 23:06
> To:
> Subject: System VMs not migrating when host down
> Hi all,
> We are testing VM HA and are having a problem with our system VMs
> (secondary storage and console) not being started up on another host when a
> host fails.
> Shouldn't the system VMs be VM HA-enabled?  Currently they are just in an
> "Alert" agent state, but never migrate.  We are currently running 4.9.3.
> Thanks
> Sean


Andrija Panić

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