[ClusterLabs] fence_apc delay?

[Ken Gaillot]

On 09/06/2016 10:20 AM, Dan Swartzendruber wrote:
> On 2016-09-06 10:59, Ken Gaillot wrote:
> 
> [snip]
> 
>> I thought power-wait was intended for this situation, where the node's
>> power supply can survive a brief outage, so a delay is needed to ensure
>> it drains. In any case, I know people are using it for that.
>>
>> Are there any drawbacks to using power-wait for this purpose, even if
>> that wasn't its original intent? Is it just that the "on" will get the
>> delay as well?
> 
> I can't speak to the first part of your question, but for me the second
> part is a definite YES.  The issue is that I want a long enough delay to
> be sure the host is D E A D and not writing to the pool anymore; but
> that delay is now multiplied by 2, and if it gets "too long", vsphere
> guests can start getting disk I/O errors...

Ah, Marek's suggestions are the best way out, then. Fence agents are
usually simple shell scripts, so adding a power-wait-off option
shouldn't be difficult.

>>> *) 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.
>>
>> FYI, no special configuration is needed for this with recent pacemaker
>> versions. If multiple devices are listed in a topology level, pacemaker
>> will automatically convert reboot requests into all-off-then-all-on.
> 
> My understanding was that applied to 1.1.14?  My CentOS 7 host has
> pacemaker 1.1.13 :(

Correct -- but most OS distributions, including CentOS, backport
specific bugfixes and features from later versions. In this case, as
long as you've applied updates (pacemaker-1.1.13-10 or later), you've
got it.