Well, I am not a Java developer so this task is beyond my ability. But I am
more than willing to work with someone to come up with a feature
description/user story and test it when it becomes available if it ever reaches
that stage.
Thanks
Yiping
On 1/12/18, 7:10 AM, "Paul Angus" <paul.an...@shapeblue.com> wrote:
It a high level that is quite possible to do. In practice there would be a
number of safety nets in place, staged moving of VMs is always a little fraught
without being able to reserve the resources ahead of time.
Are you volunteering to write it?
Kind regards,
Paul Angus
paul.an...@shapeblue.com
www.shapeblue.com
53 Chandos Place, Covent Garden, London WC2N 4HSUK
@shapeblue
-----Original Message-----
From: Yiping Zhang [mailto:yzh...@marketo.com]
Sent: 11 January 2018 19:16
To: users@cloudstack.apache.org
Subject: Re: why instance must be stopped in order to update its affinity
groups?
Paul, Marc:
Thanks for clarifying.
As cloud admin/operator, I do care about the instance’s placement and that
is why I’d like to apply affinity groups to all instances whenever possible.
It sounds like there is no fundamental technical reasons that a running
instance’s affinity group membership can’t be updated. Then why not allow this
operation? The logic could be as simple as follows:
If current host placement is compatible with new affinity group’s placement:
then
let the update succeed
else
if auto-migration is true && there is a suitable host to migrate to
then
live migrate instance to new host and update instance’s affinity
group membership
else
raise an exception
end
end
Here “auto-migrate” is controlled by a new global setting parameter, and it
is for migrating VM to another host in the same cluster. IOW, it does not
involve storage migration. If for some technical reasons that live migration
can’t be done here, then that inner “if ... else ... end” block can be reduced
to just “raise an exception”.
Is this reasonable?
Yiping
On 1/11/18, 12:19 AM, "Marc-Aurèle Brothier" <ma...@exoscale.ch> wrote:
Hi Yiping,
To add to Paul's comment, you also need to understand the goal of the
anti-affinity groups. If they don't care, you should simply block the
command so that your users don't use it (you should list the
createAffinityGroup command as a root admin call in the
commands.properties
file by changing it's flag value).
The goal is to spread a group of VMs, a cluster of a service, so that in
case of a hardware failure on one hyperisor, the cluster can be sure
that
only 1 of its instances will go down and the srvice can keep running.
On Thu, Jan 11, 2018 at 9:01 AM, Paul Angus <paul.an...@shapeblue.com>
wrote:
> Hi Yiping,
>
> Anti-affinity groups deal with the placement of VMs when they are
started,
> but doesn't/can't 'move' running VMs (it isn't like vSphere DRS). If
you
> change a VM's anti-affinity group, it's current placement on a host
may
> suddenly become invalid. As the Anti-Affinity group code isn't
designed to
> move VMs, the safest option is to ensure that the VM is stopped when
its
> group is changed so that when it is started again, CloudStack can then
> properly decide where it can/should go.
>
>
>
> Kind regards,
>
> Paul Angus
>
> paul.an...@shapeblue.com
> www.shapeblue.com
> 53 Chandos Place, Covent Garden, London WC2N 4HSUK
> @shapeblue
>
>
>
>
> -----Original Message-----
> From: Yiping Zhang [mailto:yzh...@marketo.com]
> Sent: 10 January 2018 19:51
> To: users@cloudstack.apache.org
> Subject: why instance must be stopped in order to update its affinity
> groups?
>
> Hi, List:
>
> Can someone please explain why a VM instance must be in stopped state
when
> updating its affinity group memberships? This requirement is in
“Feature
> assumptions” section of the original 4.2 design document (
> https://cwiki.apache.org/confluence/display/CLOUDSTACK/
> FS+-+Affinity-Anti-affinity+groups).
>
> My users either don’t understand or don’t care about affinity groups
and I
> see a large number of instances with sub-optimal host placement (from
> anti-host affinity group point of view). But it is too much trouble
for me
> to coordinate with so many users to shut them down in order to fix
their
> host placement. What bad things would happen if a running instance’s
> affinity group is changed?
>
> Thanks,
>
> Yiping
>
>
