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From Jon Marshall <>
Subject Re: 4.11 without Host-HA framework
Date Wed, 23 May 2018 20:09:37 GMT
Rohit / Paul

Thanks again for answering.

I am a Cisco guy with an ex Unix background but no virtualisation experience and I can honestly
say I have never felt this stupid before 😊

I have Cloudstack working but failover is killing me.

When you say VM HA relies on the host telling CS the VM is down how does that work because
if you crash the host how does it tell CS anything ? And when you say tell CS do you mean
the CS manager  ?

I guess I am just not understanding all the moving parts. I have had HOST HA working (to an
extent) although it takes a long time to failover even after tweaking the timers but the fact
that I keep finding references to people saying even without HOST HA it should failover (and
mine doesn't) makes me think I have configured it incorrectly somewhere along the line.

I have configured a compute offering with HA and I am crashing the host with the echo command
as suggested but still nothing.

I understand what you are saying Paul about it not being a good idea to rely on VM HA so I
will go back to Host HA and try to speed up failover times.

Can I ask, from your experiences, what is a realistic fail over time for CS ie. if a host
fails for example ?


From: Paul Angus <>
Sent: 23 May 2018 19:55
Subject: RE: 4.11 without Host-HA framework


As Rohit says, it is very important to understand the difference between VM HA and host HA.
VM HA relies on the HOST telling CloudStack that the VM is down on order for CloudStack start
it again (wherever that ends up being).
Any sequence of events that ends up with VM HA restarting the VM when CloudStack can't contact
the host is luck/fluke/unreliable/bad(tm)

The purpose of Host HA was to create a reliable mechanism to determine that a host has 'crashed'
and that the VMs within it are inoperative. Then take appropriate action, including ultimately
telling VM HA to restart the VM elsewhere.<>
Shapeblue - The CloudStack Company<>
ShapeBlue are the largest independent integrator of CloudStack technologies globally and are
specialists in the design and implementation of IaaS cloud infrastructures for both private
and public cloud implementations.

53 Chandos Place, Covent Garden, London  WC2N 4HSUK

-----Original Message-----
From: Rohit Yadav <>
Sent: 23 May 2018 10:45
Subject: Re: 4.11 without Host-HA framework


In the VM's compute offering, make sure that HA is ticked/enabled. Then use that HA-enabled
VM offering while deploying a VM. Around testing - it depends how you're crashing. In case
of KVM, you can try to cause host crash (example: echo c > /proc/sysrq-trigger) and see
if HA-enabled VMs gets started on a different host.

- Rohit


From: Jon Marshall <>
Sent: Tuesday, May 22, 2018 8:28:06 PM
Subject: Re: 4.11 without Host-HA framework

Hi Rohit

Thanks for responding.

I have not had much luck with HA at all.  I crash a server and nothing happens  in terms of
VMs migrating to another host. Monitoring the management log file it seems the management
server recognises the host has stopped responding to pings but doesn't think it has to do

I am currently running v4.11 with basic network but 3 separate NICs, one for management, one
for storage and one for VMs themselves.

Should it make it any difference ie. would it be worth trying to run management and storage
over the same NIC ?

I am just lost as to why I see no failover at all whereas others are reporting it works fine.


From: Rohit Yadav <>
Sent: 22 May 2018 12:12
Subject: Re: 4.11 without Host-HA framework

Hi Jon,

Yes, Host-HA is different from VM-HA and without Host HA enabled a HA enabled VM should be
recovered/run on a different host when it crashes. Historically the term 'HA' in CloudStack
is used around high availability of a VM.

Host HA as the name tries to imply is around HA of a physical hypervisor host by means of
out-of-band management technologies such as ipmi and currently supporting ipmi as OOBM and
KVM hosts with NFS storage.

- Rohit


Apache CloudStack: Open Source Cloud Computing<>
CloudStack is open source cloud computing software for creating, managing, and deploying infrastructure
cloud services

From: Jon Marshall <>
Sent: Monday, May 21, 2018 8:36:04 PM
Subject: 4.11 without Host-HA framework

I keep seeing conflicting information about this in the mailing lists and in blogs etc.

If I run 4.11 without enabling Host HA framework should HA still work if I crash a compute
node because my understanding was the new framework was added for certain cases only.

It doesn't work for me but I can find a number of people saying you don't need to enable the
new framework for it to work.


53 Chandos Place, Covent Garden, London  WC2N 4HSUK @shapeblue<>
53 Chandos Place, Covent Garden, London  WC2N 4HSUK @shapeblue

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