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

[Karli Sjöberg]

30 jul 2012 kl. 17.18 skrev Itamar Heim:

On 07/30/2012 04:25 PM, Karli Sjöberg wrote:

30 jul 2012 kl. 12.26 skrev 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.

I´m quoting you here:
"1. power management is DC wide, not cluster."

So this wouldn´t be any different from it´s current state.

true, but if you have multiple DCs, engine as a host can be used to
fence only one DC.
while if engine is 'special', it can be used to fence in all DCs

OK, so you actually want the engine to be special. Well, thats how VMWare vCenter also manages power control so I like that as well. Of course it´s always better if engine could fence all DC´s, instead of just one, and it would also make it a lot more intuitive to configure, cause you won´t need two hosts before the first could verify the other either.  And if the engine goes down, you would have bigger issues than power control to worry about;)




also, for any host other than engine, question is what to do if it is
down...



Med Vänliga Hälsningar
-------------------------------------------------------------------------------
Karli Sjöberg
Swedish University of Agricultural Sciences
Box 7079 (Visiting Address Kronåsvägen 8)
S-750 07 Uppsala, Sweden
Phone:  +46-(0)18-67 15 66
karli.sjoberg at slu.se<mailto:karli.sjoberg at slu.se> <mailto:karli.sjoberg at adm.slu.se>






Med Vänliga Hälsningar
-------------------------------------------------------------------------------
Karli Sjöberg
Swedish University of Agricultural Sciences
Box 7079 (Visiting Address Kronåsvägen 8)
S-750 07 Uppsala, Sweden
Phone:  +46-(0)18-67 15 66
karli.sjoberg at slu.se<mailto:karli.sjoberg at adm.slu.se>

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