Re: Cloud Computing

On Tue, 14 Apr 2009, Peter Duniho wrote:


That's only the case if you give up control over your data. If you want
control, keep it. For instance, if you're running a typical e-commerce
site, you can run the database housing the product catalogue etc in-house,
but run your app servers out in the cloud, with plenty of memory for
caching (or even a complete copy of the catalogue on disk, which you can
update remotely). The only network traffic will be database reads on cache
misses, and writes when orders etc are made. Terminating those kinds of
requests will be far less resource-intensive than running the entire site,
so you need far lighter in-house infrastructure, but retain complete
control (if we understand the same thing by 'control', that is).

To me, the defining aspects is instant scalability. Using something like
EC2, you can go to a webpage (or programmatically to a web service) and
enlarge your app from running on a single machine to a hundred with a
single click. And moreover, you pay for what you use - you don't have to
pay a retainer to keep those 99 extra machines available. That's what
differentiates cloud from a conventional hosting provider.

The other big differences are that cloud environments provide a richer set
of facilities than a plain host - typically a persistent mass storage
facility, possibly structured as a database of some sort, and a message
queue service.

Oh, and also, you typically don't get uptime guarantees, so you have to
structure your app in such a way that it can smoothly ride over some of
its servers vanishing with no warning! This is why the facilities are so
important - keeping all the important state in the storage service and
using the queue to manage requests helps you do this.

tom

--
I believe there is no philosophical high-road in science, with
epistemological signposts. No, we are in a jungle and find our way by
trial and error, building our road behind us as we proceed. -- Max Born