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From Marcus Sorensen <shadow...@gmail.com>
Subject Re: A question on vm migrations when hosts are set into a maintenance mode.
Date Tue, 12 Nov 2013 21:37:53 GMT
 I have done parallel KVM migrations without issue, it's "supposed to
work". Really I think it's in the same boat as parallel start/stop. It
should work, but the config option is there just in case. I think we
should add it.

On Thu, Oct 3, 2013 at 11:41 AM, Chip Childers
<chip.childers@sungard.com> wrote:
> On Thu, Oct 03, 2013 at 11:44:46AM -0500, Alex Ough wrote:
>> I'm not sure what else commands 'MigrateCommand' actually execute in
>> addition to 'Start/Stop/CopyCommand', but can we include 'MigrateCommand'
>> if it consists of only those 3 commands?
>>
>> Thanks
>> Alex Ough
>
> In the case of VMware, the migrate command is executed via the
> MigrateVMTask that's part of the VMware SDK (see
> vmware-base/src/com/cloud/hypervisor/vmware/mo/VirtualMachineMO.java).
>
> For VMware, I know that vCenter will queue and process concurrent
> requests for migrations.  Specifically, it will throttle the migrations
> happening, based on it's internal concurrency constraints, but the task
> queue will still accept more connections.  Obviously the risk are the
> VMware layer tasks timing out if it takes too long for the task queue to
> complete.
>
> As for XenServer, it's happening in what appears to be a similar way
> (although the source host is the target for the migration API call).
>
> Check
> plugins/hypervisors/xen/src/com/cloud/hypervisor/xen/resource/CitrixResourceBase.java.
>
> I'm not familiar enough with XenServer's concurrency model for
> migrations.  Any experts know the answer to if it can handle concurrency
> in a stable way?
>
> With KVM, it's obviously executing via the agent.  Similarly to
> XenServer, I'm not familiar enough to know about concurrent operations.
>
> So do the HV experts on the list have any opinions about XenServer and
> KVM migration concurrency?
>
> -chip
>
>

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