[ClusterLabs] Antw: [EXT] Fencing explanation

Reid Wahl nwahl at redhat.com
Mon Jan 4 14:07:21 EST 2021

On Mon, Jan 4, 2021 at 4:56 AM Ulrich Windl
<Ulrich.Windl at rz.uni-regensburg.de> wrote:
> >>> Ignazio Cassano <ignaziocassano at gmail.com> schrieb am 28.12.2020 um 22:21 in
> Nachricht
> <CAB7j8cVx-A5XnQ+3axD4qevrvOxniGW3ryA8Oq=UWYnsyuGo6Q at mail.gmail.com>:
> > Hello all, I am setting a pacemaker cluster with centos 7 and ipmi idrac
> > fencing devices.
> > What I did not understand is how set the number of seconds before a node is
> > rebooted by stonith.
> Actually the only reason for a delay IMHO would be:
> 1) You want to give dirty blocks a chance to be written, especially if multiple resource operations had been initiated before fencing
> 2) You want to have a look at the situation before fencing (maybe trying to clean it up to avoid fencing)
> Unsure cleaning up in 2) can really avoid fencing, but I think in HP-UX Service Guard it was possible.

The most common reason I've seen for setting a delay is to avoid a
fence race in a two-node cluster. A user can set a delay for one
node's stonith device so that both nodes don't power each other off at
the same time in the event of a network disruption.

> > If the cluster is made up 3 nodes (A, B, C) if the node C is unreacheable
> > (for example have network cards corrupetd) after how many second is
> > rebooted by stonith ?
> > Which is the parameter to set the number of seconds?
> > Sorry for my bad english
> > Thanks
> > Ignazio
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Reid Wahl, RHCA
Senior Software Maintenance Engineer, Red Hat
CEE - Platform Support Delivery - ClusterHA

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