????上周早些時候，亞馬遜（Amazon）部分云計算服務陷入癱瘓，影響到地理定位社交網站Foursquare、在線視頻網站Netflix、圖片共享網站Instagram以及數百萬用戶。雖然服務很快得以恢復，但這是亞馬遜半年以來第二次發生如此嚴重事故，不禁令人對云計算產生了諸多疑慮。

????將公司部分或全部業務遷移至云端——用行話來說，就是將數據和應用程序存放在大型遠程主機上。這種做法與依靠傳統服務器和內部IT部門相比，通常可以大幅節約成本。不過倘若云計算平臺出現上文那樣的故障，這些公司恐怕會慘遭打擊。

????云計算顯然是未來的發展趨勢。不過，云計算目前仍然需要警惕四大威脅：

穩定性

雖然亞馬遜的這次事故表明云計算也會宕機。但其發生頻率并不像你想的那樣高。Box.net是一家位于加州帕洛阿爾托市的云計算服務公司。其首席執行官阿隆?列維表示：“云計算（的穩定性）取決于用戶選擇的供應商。從許多方面來看，無論是管理內容數據還是處理電子郵件，云計算實際要比絕大部分內部平臺更為可靠和強健。”

????列維認為，云計算出現宕機通常非常少見，但更容易被外界察覺。“假如我們自己內部的IT服務突然宕機六個小時，對公司外的人而言，他們根本不會有所覺察。但由于類似這樣的宕機影響了云計算平臺服務商Heroku和視頻網站Netflix，所以一旦出事，大家很容易發覺。”

安全性

????將越來越多的數據納入云端，公司和個人是否將更容易遭遇黑客入侵和數據丟失的威脅？現在許多人仍會提出這個問題。事實是是，答案視情況而定。

????云計算安全問題伴隨Dropbox事件浮出水面。今年六月，這家位于舊金山的熱門文件同步新創企業承認，一處程序錯誤導致用戶在四個小時里可以使用錯誤密碼登陸賬號。Dropbox修復了錯誤并在博客中承認了該問題，不過Dropbox是在有用戶發現問題并表達憂慮后才采取的行動。

????其它安全問題則與代碼錯誤毫無干系。一些公司利用磁帶或磁盤備份客戶數據，在一段時間之后才會將其銷毀。弗雷斯特公司（Forrester）研究員王晨曦（音譯——譯注）最近對《財富》雜志（Fortune）透露，有家云計算供應商定期將備份的磁帶送往一家數據銷毀公司。結果有一次，數據銷毀公司遺失了所有磁帶，包括這家云計算公司的客戶保存在磁帶上的所有數據。（王并未透露公司的具體名稱）

服務器

????一些云計算供應商在同一實體服務器上存儲不同客戶的數據。所以，客戶A可能運行在一個“虛擬機”上，客戶B則運行在另一個，但所有客戶實際都運行在同一實體服務器上。經驗豐富的黑客如果獲取了客戶A的訪問權，那么他也有可能獲取客戶B的數據。王說：“這種風險可能很小，但也有可能非常致命，得取決于云計算供應商存儲數據的方式。

不知所云

????雖然云計算在科技界炙手可熱，但許多美國人仍不清楚云計算的確切含義，要么弄不清自己在那些方面使用了云計算。市場研究公司NPD Group最近的調查顯示，雖然高達76%的美國消費者在使用谷歌（Goole）Gmail和在線視頻網站Hulu等基于云計算的互聯網服務，但僅有22%的美國消費者真正明白云計算的含義。

????從發送簡單信息到觀看電影，云計算隨處可見，它已深深融入到最普遍的技術之中。隨著云計算越來越普及，很多公司可能將致力于盡可能減小上述四大威脅帶來的困擾。

????譯者：項航

????Earlier this week, portions of Amazon's cloud computing service crashed, impairing Foursquare, Netflix and Instagram as well as millions of users. While service was quickly restored, it marked the second major incident of its kind in the last six months -- and that is raising concerns with some.

????Putting parts or all of your company in the cloud -- the oft-used term to describe large, remotely hosted data sets and applications -- is typically far more cost-effective than relying on traditional servers and internal IT departments. But, incidents like these can also bring a cloud-hosted company to its knees.

????Cloud computing is obviously here to stay. But, here are four ongoing issues to watch out for as adoption rises:

Outages

????As Amazon's (AMZN) latest incident proves, outages happen. But they may not happen as frequently as you might think. "In many ways the cloud, depending on what vendor you choose, is actually more reliable and often more robust than most internal environments, whether that's for managing content or managing email," says Aaron Levie, CEO of Box.net a Palo Alto, California-based cloud services firm.

????Levie argues that cloud outages are generally rare but much more visible to the outside world. "If my own internal IT service goes down for six hours, that's not really evident to anyone outside my organization, but because something like this also took down Heroku and Netflix (NFLX), it's more apparent that something happened."

Security

????By off-loading more data to the cloud, are companies and individuals opening themselves up to hacking and data loss? That's a question many still ask. The answer, it turns out, is it depends.

????Security became an issue with popular file-syncing startup Dropbox last June when the San Francisco-based company admitted that a programming glitch allowed users to log into accounts with the wrong password over a period of four hours. The company fixed the problem and admitted the flaw in a blog post, but not before some users caught on, expressing concern.

????Other security lapses have nothing to do with coding errors. Some firms backup clients' data on tapes or disk drives, destroying them after a period of time. Forrester researcher Chenxi Wang recently told Fortune about a cloud provider which routinely sent their back-up tapes to a data disposal company. In one case, the data disposal company lost all the tapes, along with all the cloud clients' data on them. (Wang would not reveal which firm it was specifically.)

Servers

????Some cloud providers store data from several clients on the same physical server. So, Client A might be running on one "virtual machine" and Client B could be running on another, but both may actually be on the same physical server. An experienced hacker gaining access to Client A could also potentially find their way into Client B's data too. "The risk of that, depending on how the cloud provider, may be minimal, or it may be quite substantial," Wang says.

Confusion

????Though the term has gotten buzzy in the tech world, many Americans still don't quite understand the term or its implications for the way they use technology. According to a recent study from the NPD Group, just 22% of American consumers understand the concept, even though 76% of the U.S. population uses Internet including cloud-based services like Google's (GOOG) Gmail or Hulu.

????Cloud services have already worked their way into the fabric of the most common technologies, from sending simple messages to watching movies. As the services grow more and more popular, companies will likely be focusing on minimizing these four threats as much as possible.