[ClusterLabs] setting up SBD_WATCHDOG_TIMEOUT, stonith-timeout and stonith-watchdog-timeout

[emmanuel segura]

the only thing that I can say is: sbd is a realtime process

2016-12-08 11:47 GMT+01:00 Jehan-Guillaume de Rorthais <jgdr at dalibo.com>:
> Hello,
>
> While setting this various parameters, I couldn't find documentation and
> details about them. Bellow some questions.
>
> Considering the watchdog module used on a server is set up with a 30s timer
> (lets call it the wdt, the "watchdog timer"), how should
> "SBD_WATCHDOG_TIMEOUT", "stonith-timeout" and "stonith-watchdog-timeout" be set?
>
> Here is my thinking so far:
>
> "SBD_WATCHDOG_TIMEOUT < wdt". The sbd daemon should reset the timer before the
> wdt expire so the server stay alive. Online resources and default values are
> usually "SBD_WATCHDOG_TIMEOUT=5s" and "wdt=30s". But what if sbd fails to reset
> the timer multiple times (eg. because of excessive load, swap storm etc)? The
> server will not reset before random*SBD_WATCHDOG_TIMEOUT or wdt, right?
>
> "stonith-watchdog-timeout > SBD_WATCHDOG_TIMEOUT". I'm not quite sure what is
> stonith-watchdog-timeout. Is it the maximum time to wait from stonithd after it
> asked for a node fencing before it considers the watchdog was actually
> triggered and the node reseted, even with no confirmation? I suppose
> "stonith-watchdog-timeout" is mostly useful to stonithd, right?
>
> "stonith-watchdog-timeout < stonith-timeout". I understand the stonith action
> timeout should be at least greater than the wdt so stonithd will not raise a
> timeout before the wdt had a chance to exprire and reset the node. Is it right?
>
> Any other comments?
>
> Regards,
> --
> Jehan-Guillaume de Rorthais
> Dalibo
>
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