Re: another laundry or shopping list

[Alan Robertson <alanr@unix.sh>]

carlos wrote:
> 
> Jordi Polo Wrote:
> 
> > I like MOSIX approach also, in fact i think that sometimes is just necesary ,
> > but i would migrate more info and let in the home node just the minimum so
> > i'd break the depyty and migrate part of it . So if i have to send a signal i
> > can send it directly to the node where the process is. That implies the need
> > of the cache and all that thing of my last mail but eliminates  the need to
> > send 10 signals 3 lans away when the node is just next to me.
> >
> > Another little idea: what about not moving but copying the process and sleep
> > it in the home node and a little heartbeat so if the other node fails you can
> > run again the process in other node.  This obviusly is a higher lever, very
> > optional feature.
> 
> I think it's a good idea to include it as an optional issue in the
> kernel. In that way people not only would choose between HA, or HP
> cluster. People with slow lans will not choose that behaviour, but may
> be many other people will be interested in the reliability of their
> process. I like mosix approach but i think there are many systems that
> will appreciate this effort. On the other hand , the problem is not as
> easy to solve as make a heartbeat and send context and DATA dirty pages,
> first of all we should decide things like how to manage the clock of the
> system and other things like that.
> I`am thinking in that part of code as an optional code in the cluster
> system, I do not think a lot of people interested in waste a lots of
> resources in that behaviour.

A process has state internally, and migrating it is very different from
restarting it.  You can't migrate a process when a node dies - you can only
restart it.  Automatic restart of a process by the OS is probably not a good
idea.

	-- Alan Robertson
	   alanr@unix.sh

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