There is a system which uses your serial port so that if server B detects
server A goes down, it will send a signal over the serial port which
disconnects server A's power supply. That way, server B never
"accidentally" takes over for server A when in fact server A is still
running. I don't remember where these are sold, but they were mentioned
in the MissionCriticalLinux system documentation.
Jon
On Tue, 17 Jun 2003, Bruno Wolff III wrote:
> On Tue, Jun 17, 2003 at 15:41:45 +0200,
> Daniel Seichter <daniel@dseichter.de> wrote:
> > Hello Scott,
> >
> > > Are you looking more for failover, load balancing, hot
> > > spare?
> > I am looking for a hot spare, so if one server crashed, the second will
> > "spare" it, because if this database will be down (down is meant for longer
> > than 2 hours) more than two other databases will not continue working (they
> > could continue working, but without new data, so it will be senseless).
>
> Once the orignal postmaster has stopped running (say because its server
> died) you could run a different postmaster (on say another server) and
> access the same data on your storage system. But if you do this you
> will want some sort of safety system so that two postmasters can't
> accidentally run at the same time. The normal interlock won't work for you
> because it keeps a PID file and checks to see if the pid in that file (if any)
> is still running. That doesn't work accross servers.
>
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