[Phpwm] Load Balancing and redundancy

[Alex Mace]

Replication is much simpler, it can be done with just two machines. Cluster
needs at least three machines but is a very nice solution and more scalable
because you can do updates on any node, whereas with replication you really
need to do all your writes to the master and read data from the slave. Which
one is right really depends on how you're using the database. If you're
mainly doing reads then replication is probably the best solution, if it's
writes then it's probably worth having a look at Cluster...

On 22/03/07, Mike Tipping <mike at e-msg.co.uk> wrote:
>
> The db is already on a separate server...
>
> ...which again might get thrashed.
>
> My next question was going to be:
>
> MySQL Cluster or Replication or ...
>
> Cheers
>
> Mike
>
>
>
> -----Original Message-----
> From: phpwm-bounces at mailman.lug.org.uk
> [mailto:phpwm-bounces at mailman.lug.org.uk] On Behalf Of David Goodwin
> Sent: 22 March 2007 17:09
> To: West Midlands PHP User Group
> Subject: Re: [Phpwm] Load Balancing and redundancy
>
>
> > http://www.linux.com/article.pl?sid=05/07/27/1729229
> >
> > that makes it sound amazingly easy.
> >
> > The things I'm not sure about are:
> >
> > Redundancy - It can handle one of the web servers going down but what
> > happens if the balance server goes down?
> >
>
> With LVS you can protect the routing server with e.g. Heartbeat... but
> you effectively then have a minimum cluster size of 4, (2 routers, 2 web
> servers). Perhaps availability isn't a great issue?
>
> Does : http://bytemark.co.uk/page/Live/hosting/cluster/ help?
>
> > Resources - I guess you need to have an exact copy of the site on each
> > server which sounds like a headache. Linux Virtual Server utilizes a
> shared
> > data store so gets around this.
>
> Well, I don't think it would be that much of a pain. I presume you use
> some sort of versioning system (CVS, SVN etc) - so the code should be in
> sync already. Your main issue is that of sessions (and e.g. uploaded
> files). Both would need to be stored in a database, or on a shared file
> system like NFS.
>
> (How does rsync handle deletion when a file could appear on either
> server?)
>
> My gut reaction is to go for the easier 'move db to seperate box' to
> start with, as it's easy to do, with no headaches involved - although a
> cross over cable between db <-> web server would be nice.
>
> David.
>
>
> --
> David Goodwin
>
> [ david at codepoets dot co dot uk ]
> [ http://www.codepoets.co.uk       ]
>
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