紅透半邊天的Cloud Computing

Cloud Computing(雲端運算)最近真是紅透半邊天，連我們database的課程都要參一腳，有人說Cloud Computing只是個噱頭，也有人是大力推廣、好像神一般的崇拜。遲早都要會的，就趁現在把它KO掉吧！

首先，Cloud Computing絕對不是一個新的技術或程式語言什麼的，充其量的說，他是一個新的架構、新的概念。

根據wikipedia的定義：

It is a style of computing where IT-related capabilities are provided 「as a service」,^[2] allowing users to access technology-enabled services from the Internet ("in the cloud")^[3] without knowledge of, expertise with, or control over the technology infrastructure that supports them.^[4]

Times Online這樣說：

The concept, quite simply, is that vast computing resources will reside somewhere out there in the ether (rather than in your computer room) and we'll connect to them and use them as needed.

SearchSOA.com的定義是：

Cloud computing is a computing paradigm in which tasks are assigned to a combination of connections, software and services accessed over a network. This network of servers and connections is collectively known as "the cloud."

Web2.0 JOURNAL 說 :

The way I understand it, 「cloud computing」 refers to the bigger picture…basically the broad concept of using the internet to allow people to access technology-enabled services. According to Gartner, those services must be 「massively scalable」 to qualify as true 「cloud computing」. So according to that definition, every time I log into Facebook, or search for flights online, I am taking advantage of cloud computing.

ZDNET又說：

(1) Performing enormous scientific calculations in hundreds or thousands of idle machines within an enterprise or worldwide. See grid computing. See also utility computing.

(2) Running applications in or from network servers. Computing "in the cloud" may refer to a company's own network, but often refers to the Internet and the use of Web browser-based or rich client applications. It implies a trend toward thin client computing, which was embodied in the "network computer" of the late 1990s (see network computer).

For example, Google Apps provides common business applications online that are accessed from a Web browser. The software comes from the Web servers, and the data may be stored on the servers as well (see Google Apps). See cloud, SaaS, ASP, thin client and rich client.

IBM big brain Irving Wlawadsky-Berger provides a succinct definition:

「What is cloud computing? It is basically an Internet-based network made up of large numbers of servers - mostly based on open standards, modular and inexpensive. Clouds contain vast amounts of information and provide a variety of services to large numbers of people. Users of the cloud only care about the service or information they are accessing - be it from their PCs, mobile devices, or anything else connected to the Internet - not about the underlying details of how the cloud works.」

網路上還有許許多多對於Cloud Computing的解釋和定義。從這些敘述中，我們可以抓處一些關鍵字，那就是：

Internet、Enormous Computing、Resource(Service) Access

Cloud Computing可以說是透過網際網路去存取、使用一些服務或資源。這些服務或資源的背後是由許許多多科技基礎建設(Infrastructure)所建立起來的一個Cloud-Based Concept。當我們在使用這些服務或資源時，不需要瞭解背後運作的原理或建設的方式，只需要做一個連接的動作即可。透過這樣的方式，一般使用者可以輕鬆、間接使用強力運算所帶來的好處。

但是問題來了，我們不是很早就活在這樣的世界下了嗎？就算沒有早到哪裡去，至少使用Gmail、Facebook絕對不是最近幾個月的事情。為什麼這樣的概念在最近突然大紅大紫？

Cloud Computing最重要的概念就是Scalability。也就是他要能夠負擔、乘載許許多多users去存取、使用這個服務。要達到這樣的目標背後所必須依賴的架構，就是Cloud Computing所強調的概念。

早期我們使用Mail服務時，必須要知道自己的Mail Server的位置，換句話說，伺服器所服務的users是固定的。但是現在並不同，我們鍵入一個網址，連線到Yahoo Mail、GMail去存取我們的信件時，背後所連線到的server是動態的、是不固定的，主機必須要有這樣的能力去判斷不同時間、不同地點、甚至是相同使用者不同時間所面對的server都是不同的，這其中動態指向的能力也是Cloud Computing強調的重點之一。

事實上，Cloud Computing和很多概念是有密切相關的。包括：Grid Computing、Utility Computing、SaaS(Software-As-A-Service)等等。網路上也有不少文章想要嘗試說明這當中的差別，有興趣的人可以參考下面的文章：

What's In A Name? Utility vs. Cloud vs Grid What's the Difference Between Cloud Computing and SaaS? What cloud computing really means

這當中的差別當然還是有的，但我認為不是那麼重要。一般的使用者會在乎Cloud Computing和Grid Computing哪一個是比較新的概念嗎？在他們看來，這些都如同一個黑盒子(Black Box)一樣，只要服務夠水準、品質有保障，對他們還說就夠了。

在未來的發展上面，目前Cloud Computing所遭遇到最大的問題應該是標準化(standardization)和安全性(security)的問題。一項技術或protocol架構要普及，最重要的就是要標準化，有統一的規格和技術內涵、有標準的軟硬體支援，如此價格才容易下降、使用者也才可以將自己的資料隨處移動。安全性就更不用說，企業為什麼要把自己的資料放到雲端主機上？一定要有足夠的安全性來說服他們，這是最基本也是最核心的問題。

【番外篇】
目前Google "Cloud Computing"這個關鍵字共有15,600,000個搜尋結果