tpo2 at spin
Jan 28, 1998, 2:18 AM
Views: 1232
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I suppose introductions are in order now...
[In reply to]
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On Tue, 27 Jan 1998, Alex deVries wrote:
> > > > Here's the way that I'd worked it out; the servers magically have cohesive
> > > > filesystems among them so that any disk caching is synchronized. I have
> > > > no idea how to do this.
> > Make the client commit the write to all servers before returning. Reads
> > you can share around. Coping with coherency loss requires major brainwork
> > though - thats a not minor chunk of the CODA fs for example
>
> The problem with getting the client to commit everything to the servers is
> that it takes a huge performance hit. Nobody wants for their file changes
> to take a couple of seconds to flush all the local cache buffers.
>
> The one thing that I don't like about coda is that the file writes to the
> server are only done on a close(), which means that you can easily have a
> reader on another client that's not reading the most recent version.
>
> I know, I'm asking for the world. I want multiple servers all nicely
> synchronized and perfectly redundant. I want it now, and I want it free.
>
> The solution to this problem is to figure out what you want to trade off:
> synchronization, performance or redundancy.
Well I don't really think you have to trade off. Let's say f.ex. You have
a LAN and set up a 2nd 100M LAN just for synchronisation. How big will the
delays be? I think not really relevant compared to other stuff like for
example Win95 client speed, slow internet connections etc. Again, I'm
talking about "realworld" applications and not supercomper clusters
serving a mission critical nuclear station.
And allthough I haven't had a look at coda, I think it's not that
stupid to wait longer than necessary: set up >one< backup box connected
through a >fast< connection, and have it synchronized.
*
t
"This Perl language is wonderfull. Where can I get it - from Microsoft?"
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