Recently the term “Cloud–computing” (or more easy and quick “Cloud”) become not just a modern “buzz” word!
Whole a lot of companies start moving they business into the cloud(s) or plan to do so.
Many start ups initially build they solutions specially to run in the cloud.
It seems like if you working in some management position, and must predict technical future for you company (or your own) business, it’s very high probability that you already start thinking same way like companies / start ups I describe above or at least start doing huge research in that direction!
But as Mark Twain said “Whenever you find yourself on the side of the majority, it is time to pause and reflect.”, simply follow “everybody” movements can lead to significant issues in the future!
So let’s quickly discuss following questions:
(1) when and why it make sense to move into the cloud from technical / business point of view
(2) how to do migration right and “safe” way
There are a lot of well known publications about (1), because every Cloud supplier (Google, Amazon or Microsoft for example) describe that in details to gather potential customers from regular hosting / collocation providers or to push customers that own already some server farm to migrate into the Cloud. Usually answer will be something like “you should do it as soon as possible, because it increase ROI, increase scalability, decrease maintain costs … bla .. bla.. bla..” Sure in some way they are right, i.e. for most of small / middle size businesses it’s DO make sense to migrate into clouds, unless they already invest a LOT into existed infrastructure (both hardware and software). But what is not acceptable is fact that some people (management, but not without pushing from low levels sometimes, i.e. from engineers) start really think / believe that (2) really does not make any big difference! I.e. just fact that you start migration and understand why to do it ASAP (ROI, bla bla bla) will lead your business to new levels, will save you a lot of money, will scale you to Google scale etc!
WRONG! It make absolutely critical difference HOW you migrate (2)!
Why its SO important HOW to do it? Lets give few reasons:
a) Most of cloud solutions require payments BY amount of requests (see Azure, Amazon RDS, Google storages etc), not just hourly rates!
And this can KILL some kind of businesses, if not to say MOST of the businesses!
It simply keep telling you something like: “you can’t scale PER customer actions because for each action from now on you should PAY”!
You pay when your customer come to each page that require trip to the database! Its not, it’s ABSOLUTELY different to situation that you have with hosting / collocation! From now on, you should optimize you data access, message queues not just to be able to scale, but to save COSTS for requests! Yep, most of clouds give you very CHEAP storage space, but they get much more from you because of millions of requests you get from customers that do not pay you PER page view in most of the cases!
Think for example situation that you have jobs board and your customers (companies usually) pay you when they add new vacancy! Does it make sense for you to pay for millions of search (browsing) users (you pay per each request to Cloud supplier), if you get money only from few people who post vacancies? And you should pay not only traffic (like it was with hosting providers), from now on in the cloud you should pay for search engine queries (requests to Solr / Lucene on multiple nodes for example), for MapReduce engine, for requests into database storage (distributed hashtable or SQL database engine.. you still pay PER request) etc!
So? Before even consider moving into cloud you should think about all above and check is it will work for you! Even if you absolutely sure that it will, you anyway should care A LOT about code quality and additional features like distributed caching, replication effectiveness, traffic compressions etc! You should in most cases avoid many of such “hard” things in regular applications, but you simply can’t ignore them for most of real life application that should work in the Cloud!
b) You should migrate (or develop from begging) systems the way that they will be able to work OUTSIDE cloud! Why? Easy!
You do not have FULL control over your cloud supplier:
- It possible that supplier (Amazon, Google, MSFT or any other) will change prices or add additional fees
- It’s possible that you will want to migrate to different supplier tomorrow because it’s cheaper, or buy your own servers farm or / and even want to run OWN cloud (see Cloud.com).
- It’s possible that you will figure out that you was wrong with (1) above, i.e. you was think that you CAN afford to pay PER request, but was wrong and your servers get so huge traffic that your bills to cloud supplier quickly become not acceptable!
- etc
In all situations like above, it’s CRITICAL to be able to made a SWITCH! And that is what most of companies MISS! They simple couple technology into one Cloud supplier and did not have “back door” to quit!
From technical point of view (but sure it’s theme for different, dedicated post) you should design your architecture the way that your solution will work at least on dedicated servers farm in addition to selected Cloud. If you start using Azure Table Storage, Amazon SimpleDb or another other “cloud” specific data storage, make sure that you can execute your code on for example MongoDB, RavenDB or Cassandra and only then add support for Cloud storage! In case if you already have system that work locally (i.e. on regular dedicated server), you should make sure that you do not “broke” this functionality when start migration! And so on…
Sure it’s not all, I have much more to say about it. But it’s just enough to start at least think right way about life in the Clouds 
