[Rails] question about host web based application using rails

[Michael Koziarski]

I apologise in advance for mentioning java stuff,  but It's
interesting that you mention EBay.  Their architecture revolves around
multiple databases and a completely stateless system.

http://www.manageability.org/blog/stuff/about-ebays-architecture/view

"What enables our horizontal scalability is content based routing. So,
if imagine eBay has on any given day 60 million items. We do not want
to store that in one behemoth Sun machine. [snip] let us scale it
across; may be, many Sun machines, but how you get to the right one?
There is the content-based routing idea that comes in play. So, the
idea was that given some hint, find out which of my 20 physical
database hosts do I need to go to. The other cool thing about this is
that failover could be defined."


On Tue, 04 Jan 2005 16:14:53 -0800, Carl Youngblood <carlwork at ycs.biz> wrote:
> Joe Van Dyk wrote:
> 
> >Why do you think you need multiple databases?
> >
> I know this is somewhat late, but I have some experience with a massive
> multiple database system where each user's information had the potential
> of residing on a separate database.  Our load was so intense that it was
> ridiculously expensive to "scale up" to a larger big-iron database
> server.  Instead we devised a "scale-out" load-balancing scheme that
> used a user's username to determine which database their data was on and
> connected to that for each request.  user-db mappings were stored in
> memory in a dynamic trie structure that could be accessed with custom
> PHP functions.  Tables holding infrequently-updated common data were
> duplicated on each host and synchronized when necessary.  Transferring
> user data to a different server when load got too high had too be
> accomplished programmatically, since we had inter-server transactions in
> MySQL.  In short, it was complicated, but it did work and it saved us a
> lot of money.  This was for a web analytics product where our servers
> got a hit every time someone accessed our clients' web sites, one of
> which was eBay, for example.  That may give you some notion of the
> magnitude of the problem.  So for some specialized cases, a multiple
> database strategy can be very useful.
> 
> Carl
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-- 
Cheers

Koz