[Beowulf] using watchdog timers to reboot a hung system
automagically: Good idea or bad?
kabbey at biomaps.rutgers.edu
Thu Oct 22 19:03:58 PDT 2009
I tried this on a Supermicro board and a Sun box. On both systems the
system would reboot randomly so I tuned it off. This is a serious
problem of false positives. In a cluster, you may need to notify the
scheduler in someway when a node reboots. Can someone elaborate on
this? Specifically for torque, PBS and Sun GE.
Have you guys used watchdog timers? Maybe there is a way to build a
circuit-breaker around the principle so that if a node reboots
automatically more than 3 times then watchdog gives up?
It would far simpler to request the vendor to program thier firmware to
log each reboot and set a limitation there as well as event
notifications via email, snmp or other means. The more configurable the
Rahul Nabar wrote:
> I wanted to get some opinions about if watchdog timers are a good idea
> or not. I came across watchdogs again when reading through my IPMI
> manual. In principle it sounds neat: If the system hangs then get it
> to reboot after, say, 5 minutes automatically. But, in practice, maybe
> it is a terrible idea.
> Of course, one might say, a well configured HPC compute-node
> shouldn't be getting to a hung point anyways; but in-practice I see a
> few nodes every month that can be resurrected by a simple reboot.
> Admittedly these nodes are quite senile.
> The danger, seems to me: What if a node kept crashing (due to say, a
> bad HDD or something). Then a watchdog would merely keep rebooting
> this node a hundred times. Not such a good thing.
> Have you guys used watchdog timers? Maybe there is a way to build a
> circuit-breaker around the principle so that if a node reboots
> automatically more than 3 times then watchdog gives up?
> If one had to do the watchdogging should one do the resets locally
> using the IPMI local interface (hogs cpu cycles) or a central
> Nagios-like system that could issue such a command. Many scenarios
> seem possible. The prospect of a automated system doing a reboot at
> 3am seems more tempting than me having to do this manually.
Kevin C. Abbey
Rutgers University - BioMaPS Institute
Email: kabbey at biomaps.rutgers.edu
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