[ClusterLabs] Antw: Re: fence_apc delay?

Dan Swartzendruber dswartz at druber.com
Mon Sep 5 09:47:35 EDT 2016

On 2016-09-05 03:04, Ulrich Windl wrote:
>>>> Marek Grac <mgrac at redhat.com> schrieb am 03.09.2016 um 14:41 in 
>>>> Nachricht
> <CA+40=JWs_6hjgLaJCSZAqa6o9RqH79OA9aQ150z1+5Kjst_niQ at mail.gmail.com>:
>> Hi,
>> There are two problems mentioned in the email.
>> 1) power-wait
>> Power-wait is a quite advanced option and there are only few fence
>> devices/agent where it makes sense. And only because the HW/firmware 
>> on the
>> device is somewhat broken. Basically, when we execute power ON/OFF
>> operation, we wait for power-wait seconds before we send next command. 
>> I
>> don't remember any issue with APC and this kind of problems.
>> 2) the only theory I could come up with was that maybe the fencing
>> operation was considered complete too quickly?
>> That is virtually not possible. Even when power ON/OFF is 
>> asynchronous, we
>> test status of device and fence agent wait until status of the 
>> plug/VM/...
>> matches what user wants.
> I can imagine that a powerful power supply can deliver up to one
> second of power even if the mains is disconnected. If the cluster is
> very quick after fencing, it might be a problem. I'd suggest a 5 to 10
> second delay between fencing action and cluster reaction.

Ulrich, please see the response I just posted to Marek.  Thanks!

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