In response to Michael Gruetzner <mgruetzn at HTWM.De>:

> Hi Bill,
> 
> thank you for your detailed reply. There is yet another issue
> that I need to be aware of: network partitions. Since I can't
> ensure that all sites are connected directly, I belive that this
> kind of failure is a possible scenario.
> Do you have any idea, how Slony deals with that kind of issue?

I don't understand the question.  What do you mean by "network
partition" and how does this represent a failure scenario?

> 
> Best regards,
> Michael
> 
> On 20.04.2008, at 18:31, Bill Moran wrote:
> 
> > Michael Gruetzner <mgruetzn at HTWM.De> wrote:
> >>
> >> Hi,
> >>
> >> I have to meet the challenge of creating a wide area database  
> >> cluster.
> >> Since
> >> I have made some good experiences with Slony-1 in the past, I'm
> >> wondering
> >> if it would also work with wide-area networks. Of course, bandwidth
> >> and latency
> >> are main issues but also network failures.
> >> The Slony-1 documetation says that it might not be suitable if some
> >> nodes may
> >> fail oftenly but it does not explain how slony deals with such
> >> failures (maybe someone
> >> can explain this to me?).
> >>
> >> So what I'm asking is: Does anyone have experience with Slony-1 and
> >> wide area
> >> clusters?
> >
> > Yes.  My opinion is that it works well for typical cases.
> >
> > Network failures are a problem for a few reasons:
> > 1) It can take Slony a bit to find its feet again after a network  
> > failure.
> >   So if you have frequent failures, Slony can get into a situation  
> > where
> >   it can't get caught back up.
> > 2) Slony tends to bomb the slaves with lots of bandwidth when they  
> > come
> >   back online after an outage.  This can (potentially) be a problem if
> >   your bandwidth is limited and it fills up the pipe, interfering with
> >   other types of traffic.
> > 3) During an outage, Slony has to track all changes until the slave  
> > comes
> >   back online.  This can use up a lot of disk space pretty quickly, so
> >   an extended outage can be a real issue if you don't size your  
> > hardware
> >   to account for it.
> >
> > It's a vague question with a vague answer, because whether or not it  
> > will
> > work for you is a combination of many factors: how much spare  
> > bandwidth
> > do you have?  How frequent are the outages?  How much updating is  
> > occurring?
> > How much update lag is acceptable in the slaves during an outage,  
> > and how
> > much lag to getting caught back up after an outage is acceptable?   
> > Can you
> > size your disks to be large enough to backlog an outages worth of  
> > updates
> > while the network is down?
> >
> > If you can get all those issues into a range that's acceptable for  
> > you,
> > then Slony will meet your needs, but there are too many questions and
> > too many details to be able to provide a pat answer like "yes" or  
> > "no".
> >
> > -- 
> > Bill Moran
> > Collaborative Fusion Inc.
> >
> > wmoran at collaborativefusion.com
> > Phone: 412-422-3463x4023
> > _______________________________________________
> > Slony1-general mailing list
> > Slony1-general at lists.slony.info
> > http://lists.slony.info/mailman/listinfo/slony1-general
> 


-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran at collaborativefusion.com
Phone: 412-422-3463x4023