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From "Jeremy Brooks" <jbroo...@austin.rr.com>
Subject RE: clusters
Date Tue, 09 May 2006 16:28:18 GMT
There's also clustering in MySQL 5 that looks very enticing to me as an
additional layer or scale out and redundancy.  It's not your typical
master/slave scenario and actaully allows for real load balancing and
failover.

> -----Original Message-----
> From: Jeremy Brooks [mailto:jbrooks4@austin.rr.com] 
> Sent: Tuesday, May 09, 2006 11:19 AM
> To: 'Jeremy Brooks'; 'Perrin Harkins'; 'Ken Perl'
> Cc: modperl@perl.apache.org
> Subject: RE: clusters
> 
> As a caveat to the E-mails about caching pages using a proxy, 
> the usefulness of such depends on how much traffic your site 
> will see to static pages.  In our situation, the only static 
> pages are our "contact us" page, "privacy policy" ,etc.  
> Those pages don't get enough traffic to justify the 
> maintenance of setup overhead of a proxy. Our main page is 
> not static and neither are the product and category pages.  
> Actually over 99% of our pages are dynamic with rotating 
> specials and such.  The usefulness of caching on pages via a 
> proxy also depends on your typical landing pages.
> If you have a customer click to your site to a page with 
> dynamic content (specials, session IDs in form data, etc) 
> then caching to the most frequently viewed pages is useless 
> and even damaging/problematic.  
> 
> Regarding Round Robin DNS, this scenario will become a 
> nightmare should you loose a server that is not redundant on 
> the same IP.  Even with a very short TTL, your customers will 
> see more downtime then they like and may go elsewhere should 
> you loose a server.  DNS load balancing is generally not a 
> wise load balancing method because it's NOT actually 
> balancing load in real time.
> The affect of round robin DNS is something akin to breaking 
> up load sometime last week and hoping it all works out today. 
> It's not really an active solution since servers die and 
> nothing changes in the customers view for quite sometime.  In 
> fact, TTL must be reached before other DNS servers update 
> their cache and most importantly, your customers PC must 
> actually begin to us the new IP to connect!  So, now you're 
> dependent on DNS client
> caching on your customers PCs...   Not good.  On a Windows PC 
> this can mean
> restarting the browser, on an OSX machine this may mean 
> restarting the damn machine (really, I've experienced this).
> 
> Go with IPVS as a base and proxy if it makes sense.  Use DNS 
> load balancing only if you have redundancy on each node 
> connected to each IP and if load balancing public IPs is to 
> much pain otherwise.  
> 
> You can use IPVS in several different topologies or you can 
> mix them to get what you want.
> 
> http://www.ultramonkey.org/3/topologies/ 
> 
> 
> -Jeremy Brooks
> 
> 
> > -----Original Message-----
> > From: Jeremy Brooks [mailto:jbrooks4@austin.rr.com]
> > Sent: Tuesday, May 09, 2006 10:26 AM
> > To: 'Perrin Harkins'; 'Ken Perl'
> > Cc: modperl@perl.apache.org
> > Subject: RE: clusters
> > 
> > We use Ultra Monkey (IPVS) to cluster our E-com site with commodity 
> > hardware.
> > Your application needs to cache sessions in a common 
> database table in 
> > order to make session work consistantly.
> > 
> >  
> > 
> > > -----Original Message-----
> > > From: Perrin Harkins [mailto:perrin@elem.com]
> > > Sent: Tuesday, May 09, 2006 7:28 AM
> > > To: Ken Perl
> > > Cc: modperl@perl.apache.org
> > > Subject: Re: clusters
> > > 
> > > Ken Perl wrote:
> > > > Is it possible to make a modperl application to run in cluster?
> > > 
> > > Of course.
> > > 
> > > > if yes, how to do that?
> > > 
> > > The same as any other web system -- multiple machines, a load 
> > > balancer, shared data on a database or other system.
> > > 
> > > > any doc?
> > > 
> > > Tons of them.  Practically any doc about clustering will 
> apply.  I 
> > > wrote one ages ago about one mod_perl site I worked at:
> > > http://perl.apache.org/docs/tutorials/apps/scale_etoys/etoys.html
> > > 
> > > Is there some specific part you're having trouble getting 
> your head 
> > > around?
> > > 
> > > - Perrin
> 


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