To clarify, example #2 in the faq: redundant power feeds, redundant APCs
- no single point of failure. Provides High availability but complicates
fencing and race prevention.
This necessitates two power switch logins to successfully fence. I'll
test by manually logging in to one device and tell luci to fence a node.
With my manual login getting in the way, the fence operation should fail
and turn off no ports and not prevent manual login to other apc, no
matter which switch I manually log into. I haven't got a chance to test
this yet and I wanted to tap into your wisdom to test my logic.
thanks
scottb
Chris Harms wrote:
We have our APC power strips group the 2 ports together. The fence
agent should login to only one IP and turn off the grouped ports
instead of logging in to each unit separately to turn off power.
Scott Becker wrote:
In the FAQ, Fencing Questions
13. What's the right way to configure fencing when I have redundant
power supplies?
I'm going to setup the second example.
My concern is about a race condition with the two devices:
|<device name="pwr01" option="off" switch="1" port="1"/>
<device name="pwr02" option="off" switch="1" port="1"/>|
If I had only one power switch, the first node to login successfully
turns the other off (APC with one IP address). My concern is with two
APCs, that whoever loses the race to login to APC #1 may win the race
to login to APC #2 and then each will turn off only one of the
other's power supplies.
Is the fencing execution script designed to 1) perform all necessary
fencing device logins successfully then and only then 2) issue the
poweroff commands? Thereby averting a potential race because the
loser of the race for APC #1 will give up and hand over device #2.
thanks
newby
scottb
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