Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!uflorida!travis!hrshcx!steved
From: steved@hrshcx.csd.harris.com (Steve Daukas)
Newsgroups: comp.realtime
Subject: Re: Realtime and fault-tolerance together?
Message-ID: <848@hrshcx.csd.harris.com>
Date: 5 Nov 90 21:38:46 GMT
References: <720@dynasys.UUCP>
Organization: Harris Computer Systems - Fort Lauderdale, Fl.
Lines: 32
Location: New Hampshire

In article <720@dynasys.UUCP>, jessea@dynasys.UUCP (Jesse W. Asher) writes:
> I was wondering if any realtime operating systems also incorporated
> fault-tolerant considerations.  If so, how are they implemented software-wise?
> How do hardware based fault-tolerance systems interact with software based
> realtime?  It seems to me that they go hand in hand in many cases and that
> one would want to implement both in a system.

What do *you* mean by fault tolerance?  I've seen requirements were
a company would have to pay fines on the order of $20,000 a minute for
down-time.  In this case, you need a duplicate or triplicate system
with shared disks, etc., so that when something fails in one system,
you switch to the other.

One might define fault tolerance as the abiliy to be self correcting
in the sense of exception handeling...

In any case, the operating system usually doesn't have direct control
over the fault tolerance.  Its usually a matter of using the proper hooks
in the OS to provide for whatever capabilities make sense for the given
application.

I guess the next question is: what do *you* mean by real-time?  Are we
talking miliseconds or microseconds for response times?

Steve
--

Stephen C. Daukas              | sdaukas@csd.harris.com  
Harris Corporation             | uunet!hcx1!misg!sdaukas  
Computer Systems Division      | (617) 221-1834, (617) 221-1830

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