[ovirt-users] question regarding fencing proxies

[cmc]

Thanks Martin. That is what I assumed was the case, but got worried
when the host could not communicate with the idrac via the 'Test'
option in the GUI. I planned to test it when I get a chance by
migrating all VMs bar one to the other host, setting the remaining one
as HA, and then bringing that host down to see if it gets migrated
successfully. I do plan to add a 3rd host.

I was looking at adding an APC agent as well. Can you tell me whether
4.x supports 2 PDUs per host? We have diverse power on each server. I
saw a post in 2012 that only one was supported and didn't see an
option for adding two slots in the GUI.

Thanks,

Cam

On Sat, Jan 14, 2017 at 12:07 PM, Martin Perina <mperina at redhat.com> wrote:
> Hi,
>
> engine executes power management (fencing) operation using different host in
> the same cluster/DC as target host reside. It's an oVirt requirement that
> each host in the same cluster and data center is able to connect to power
> management deviced of all other hosts in the same cluster/DC.
>
>
> Here's simplified flow for defaults (fence proxy may be selected in the same
> cluster or DC)
>
> 1. Find all existing hosts in the same cluster which don't have connection
> issues (status Up, Maintenance, NonOperational for a reason different than
> network issues)
> 2. Select first host in Up (if no host is Up, then pick any other host, if
> no host found continue with DC in step 5) and try to execute fence operation
> 3. If fence operation is successful, exit
> 4. If not, retry 2 times and if still not successful go back to step 2 but
> exclude already problematic fence proxy
> 5. Find all existing hosts in the same data center which don't have
> connection issues (status Up, Maintenance, NonOperational for a reason
> different than network issues)
> 6. Select first host in Up (if no host is Up, then pick any other host, if
> no host found then fail and exit) and try to execute fence operation
> 7. If fence operation is successful, exit
> 8. If not, retry 2 times and if still not successful go back to step 6 but
> exclude already problematic fence proxy
> 9. If still no success, fail
>
> As you see your setup with only 2 hosts is kinda fragile (and not only for
> fencing operations), you need to assure that 1 hosts is always in perfect
> condition. If possible I'd recommend you to add at least one other host if
> possible to make your setup more resistant to failures.
>
> Martin Perina
>
>
> On Fri, Jan 13, 2017 at 6:10 PM, cmc <iucounu at gmail.com> wrote:
>>
>> Hi,
>>
>> Can someone tell me how the engine decides which power management
>> proxy/proxies to use (using default cluster/dc config)? I am using
>> drac 7 for a fence agent in my two host cluster, and have noticed that
>> one of the hosts cannot contact the drac. My guess is that the engine
>> is using one host to as a power management proxy and hosts cannot
>> reach their own drac as they are on the same interface + vlan.
>>
>> Example scenario:
>>
>> Engine uses host 2 as power management proxy. It can contact host 1’s
>> drac, but cannot contact its own drac. In the case of host 2 being
>> unreachable/kdumping etc, would the engine switch to use host 1 as the
>> proxy to contact host 2’s drac?
>>
>> Thanks,
>>
>> Cam
>>
>> PS: I'd like to use the APC as an additional fencing agent, each host
>> has two PSUs connected to two different APCs. Is there a guide on how
>> to specify two ports on two different PDUs to control power on a host?
>> _______________________________________________
>> Users mailing list
>> Users at ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/users
>
>