[ClusterLabs] fence_apc delay?

Marek Grac mgrac at redhat.com
Mon Sep 5 10:38:51 EDT 2016


On Mon, Sep 5, 2016 at 3:46 PM, Dan Swartzendruber <dswartz at druber.com>

> ...
> Marek, thanks.  I have tested repeatedly (8 or so times with disk writes
> in progress) with 5-7 seconds and have had no corruption.  My only issue
> with using power_wait here (possibly I am misunderstanding this) is that
> the default action is 'reboot' which I *think* is 'power off, then power
> on'.  e.g. two operations to the fencing device.  The only place I need a
> delay though, is after the power off operation - doing so after power on is
> just wasted time that the resource is offline before the other node takes
> it over.  Am I misunderstanding this?  Thanks!

You are right. Default sequence for reboot is:

get status, power off, delay(power-wait), get status [repeat until OFF],
power on, delay(power-wait), get status [repeat until ON].

The power-wait was introduced because some devices respond with strange
values when they are asked too soon after power change. It was not intended
to be used in a way that you propose. Possible solutions:

*) Configure fence device to not use reboot but OFF, ON
Very same to the situation when there are multiple power circuits; you have
to switch them all OFF and afterwards turn them ON.

*) Add a new option power-wait-off that will be used only in OFF case (and
will override power-wait). It should be quite easy to do. Just, send us PR.

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