[Users] RFE: A manual way of saying that only hostA in a DC shall be used as proxy for power commands

[Itamar Heim]

On 07/30/2012 12:03 PM, Karli Sjöberg wrote:
>
> 30 jul 2012 kl. 11.01 skrev Itamar Heim:
>
>> On 07/30/2012 08:56 AM, Karli Sjöberg wrote:
>>>
>>> 28 jul 2012 kl. 14.11 skrev Moti Asayag:
>>>
>>>> On 07/26/2012 02:53 PM, Karli Sjöberg wrote:
>>>>> Hi,
>>>>>
>>>>> In my DC, I have three hosts added:
>>>>>
>>>>> hostA
>>>>> hostB
>>>>> hostC
>>>>>
>>>>> I want a way to force only to use hostA as a proxy for power commands.
>>>>
>>>> The algorithm of selection a host to act as a proxy for PM commands is
>>>> quite naive: any host from the system with status UP.
>>>>
>>>> You can see how it is being selected in FencingExecutor.FindVdsToFence()
>>>> from
>>>> ovirt-engine/backend/manager/modules/bll/src/main/java/org/ovirt/engine/core/bll/FencingExecutor.java
>>>>
>>>> There is no other algorithm for the selection at the moment.
>>>>
>>>> How would you handle a case in which hostA isn't responsive ? Wouldn't
>>>> you prefer trying to perform the fencing using other available host ?
>>>
>>>
>>> Let me explain a little to make you better understand my reasoning
>>> behind this configuration.
>>>
>>> We work with segmented, separated networks. One network for public
>>> access, one for storage traffic, one for management and so on. That
>>> means that if the nodes themselves have to do their own
>>> power-management, the nodes would require three interfaces each, and the
>>> metal we are using for hosts just don´t have that. But if we can use the
>>> engine to do that, the hosts would only require two interfaces, which
>>> most 1U servers are equipped with as standard (plus one
>>> iLO/IPMI/whatev), so we can use them as hosts without issue. Then the
>>> backend has one extra interface that it can use to communicate over the
>>> power management network to the respective service processor with.
>>>
>>> Is there a "better" way to achieve what we are aiming for? Ideally, I
>>> would like to set up the two NICs in a bond and create VLAN-interfaces
>>> on top of that bond. That way, I can have as many virtual interfaces as
>>> I want without having more than two physical NICs, but I haven´t been
>>> able to find a good HOWTO explaining the process.
>>>
>>
>> I think there is a difference between:
>> 1. allowing engine to fence
>> 2. allowing to choose fencing host per cluster (or per host)
>>
>> it sounds like you actually want #1, but can live with #2, by installing
>> the engine as a host as well.
>
> Exactly, I can live with #2, as I have the engine added as hostA in my DC

well, the question is if choosing another host to use for fencing 
would/should be limited to hosts from same DC, then engine can only be 
used to fence one DC.
also, for any host other than engine, question is what to do if it is 
down...