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From Alex Ough <alex.o...@sungard.com>
Subject Re: A question on vm migrations when hosts are set into a maintenance mode.
Date Wed, 13 Nov 2013 16:21:55 GMT
All,

While merging my changes to 4.3 branch, I found that the option,
'execute.in.sequence.hypervisor.commands' is NOT used in Start/Stop/Copy
commands in 'VirtualMachineManagerImpl.java' any more as below.


*StopCommand stop = new StopCommand(vm, getExecuteInSequence());*

*protected boolean getExecuteInSequence() {*
*     return false;*
*}*

As you see in the above, the function, 'getExecuteInSequence', just returns
false instead of getting the value from the global variable.

And one more change is that the file has been moved to
'engine/orchestration/src/com/cloud/vm' from 'server/src/com/cloud/vm'.

Am I missing something related with this or do we stop supporting this
option in 4.3?
I'm a little confused, so please help me resolve this.

Thanks
Alex Ough




On Tue, Nov 12, 2013 at 4:20 PM, Alex Ough <alex.ough@sungard.com> wrote:

> Thanks a lot for your confirmation, Marcus.
> I'll create a review request unless anyone has an objection.
>
> Thanks
> Alex Ough
>
>
> On Tue, Nov 12, 2013 at 3:37 PM, Marcus Sorensen <shadowsor@gmail.com>wrote:
>
>>  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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