Failover cluster for webserver with dynamic content ?

Feczak Szabolcs feczo at siodigit.hu
Sat Apr 23 02:33:40 PDT 2005


On p, 2005-04-22 at 18:11 -0600, soralx at cydem.org wrote:
> > Anyway one step further, my question is
> > How can I create a failover cluster with two machines
> > for a freebsd webserver with dynamic content
> > runing  apache with php, and postgresql.
> 
> why can't you have 2 separate machines accessing one mirrored RAID?
> can't this give you enough redundancy?

I thought about this, but I have several fears with that.
First of all which machine would serve the RAID ?
If this machine fails, than even though I have the second
machine no use of it, since it does not have access to the data
anymore. Second: how do I sync the sql database ... even
though they use the same filesystem, some caching happens
and when one of them writes back earlier what happens when
to the other one tries to fsync. Although I do not have
deep understanding of the postgresql system I have a fear
that this threatens the data consistency. 



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