[Catalyst] FW: Clustering catalyst apps

[Perrin Harkins]

On Mon, 2006-05-08 at 14:45 +0200, Gert Burger wrote:
> I have looked at the High Availability systems that have been written
> for linux and they provide doubles(Or more) of everything, from load
> balancers to db servers. The issue I have with them are they require a
> great deal of money in hardware to get running.

You can't get high-availability for nothing.

> Anycase, back to my issue, How do websites like slashdot and amazon, all
> which use perl, keep uptimes of close to 99.999% ?
> 
> And is it possible to get to that level with lots of crappy hardware?

I don't think Slashdot can be considered highly available, but that's
beside the point.  Yahoo, Google, etc. all get high-availability on
mostly cheap hardware, but they have the scale to buy lots of it and put
a lot of effort into making it work.  If your budget is relatively low,
you will probably get more reliability by spending more on your key
components (the database server, the load balancer), since you won't
want to pay for lots of redundant hardware.  In other words, if you
aren't willing to buy doubles of everything, buy better hardware so it
is less likely to fail.

You can't expect miracles though -- real high availability is achieved
by having redundant hardware, hiring skilled personnel, and repeatedly
testing your failover plan.  That's how the companies you mentioned do
it.

Slashdot doesn't need real high-availability so they have adopted a
strategy that might be more applicable to you, i.e. better hardware but
less of it.  It's described here:
http://slashdot.org/faq/tech.shtml#te050

- Perrin