[rescue] web server loadbalancing...

[David Cantrell]

Patrick Giagnocavo <patrick at zill.net> wrote:
>>> There could well be other ways to get what you want, without having to
>>> futz around with balancing.
> 
> Like, for instance, if they just care about not having a lot of downtime:
> 
> have 2 machines, identical in every way, on-site; with no internal drives
> +
> external RAID array (battery backed cache, etc)
> 
> if first machine fails for any reason, unplug the first and hook up the
> second.  Boot from external array.  Downtime would be maybe 5 minutes,
> probably less.

You are assuming that there is someone on site who could do this.  Lots of
big sites do not have this.  Sure, there are people on site, but they don't
have access to the racks for reasons of security.  And in plenty of
instances, even 5 minutes of downtime is unacceptable.  As far as *we* are
concerned, no downtime is acceptable.  So we have redundant everything.
And speaking as an ordinary user, then five minutes of downtime is also
unacceptable and I will go elsewhere.

You also don't know how much traffic Bill's client is going to get.  I
can point you at plenty of sites which get more traffic than any single
server can realistically deal with.  Then there are other reasons for
load-balancing too, even if a single machine *could* cope.  For example,
you might want to have servers on two continents so that users in both
places get a snappy response.  Of course, if you're using all your
capacity on one continent and the other is not heavily loaded, you would
want the excess load to go to the other continent.

-- 
David Cantrell | david at cantrell.org.uk | http://www.cantrell.org.uk/david

Do not be afraid of cooking, as your ingredients will know and misbehave
   -- Fergus Henderson