Rohit,
Thanks for the effort you have put in writing the FS. I have some questions
based on my initial reading of the FS.
1. “Host HA” – In the FS you are talking about a generic HA framework but it is
not clear what is meaning of “host HA”. Is it something like all or some VMs
running on a host will be started on another host(s) in case of a failure or is
it something else? How is it different from the existing “VM HA” that is
already there?
2. You have mentioned that “Cloudstack lacks a way to reliably fence host”.
Cloudstack considers VM as a 1st class object and so provides fencing for VM
instead of host. There are hypervisor specific plugins that implement mechanism
to fence a VM. I am not sure if it makes sense to expose host fencing as end
user doesn’t care about it. Now the VM fencing implementation can use something
like “host fencing” internally.
3. There is an existing HA framework which provides plugins for doing
investigation if a VM is alive or not, host is alive or not, fencing of VM in
case it is not alive. It will be good to understand the limitations of the
existing framework and how the new framework helps in solving these problems.
We also need to understand if the limitation is in the framework or some
specific plugin implementation that is causing issues. Reference to JIRA issues
would help.
4. You have mentioned about ipmi to investigate host failure. I would like to
understand why same can’t be used in the existing framework.
Thanks,
Koushik
On 16/02/17, 4:48 PM, "Rohit Yadav" <rohit.ya...@shapeblue.com> wrote:
All,
I would like to start discussion on a new feature - Host HA for CloudStack.
CloudStack lacks a way to reliably fence a host, the idea of the host-ha
feature is to provide a general purpose HA framework and HA provider
implementation specific for hypervisor that can use additional mechanism such
as OOBM (ipmi based power management) to reliably investigate, recover and
fence a host. This feature can handle scenarios associated with server crash
issues and reliable fencing of hosts and HA of VM. The first version will have
HA provider implementation for KVM (and for simulator to test the framework
implementation, and write marvin tests that can validate the feature on Travis
and others).
Please have a look at the FS here:
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Host+HA
Looking forward to your comments and questions.
Regards.
rohit.ya...@shapeblue.com
www.shapeblue.com
53 Chandos Place, Covent Garden, London WC2N 4HSUK
@shapeblue
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