Cloud computing brings great promise, but also confusion to the IT industry. Key questions are answered here.
每个人都在IT行业都在谈论云计算，但仍有大约云是什么，应该如何使用，有什么问题和挑战可能会带来混乱。本FAQ将回答一些的企业都在问关于云计算的关键问题。
What is cloud computing?
Gartner definescloud computingas "a style of computing in which massively scalable IT-related capabilities are provided 'as a service' using Internet technologies to multiple external customers." Beyond the Gartner definition, clouds are marked by self-service interfaces that let customers acquire resources at any time and get rid of them the instant they are no longer needed.
云是不是一个真正的技术本身。相反，它是建立IT，运用快速增加服务器马力以及虚拟化技术相结合的多台服务器到大型计算池和划分单一服务器成可纺起来，随意断电多个虚拟机服务的方法。
云计算如何从效用不同，点播和网格计算？
Cloud by its nature is "on-demand" and includes attributes previously associated with utility and grid models. Grid computing is the ability to harness large collections of independent compute resources to perform large tasks, and utility is metered consumption of IT services, says Kristof Kloeckner, the cloud computing software chief atIBM。该走到一起，这些属性是使云当今最“令人振奋的IT交付模式，”他说。
Fundamentally, the phrase cloud computing is interchangeable with utility computing, says尼古拉斯·卡尔, author of "The Big Switch" and "Does IT Matter?" The word "cloud" doesn't really communicate what cloud computing is, while the word "utility" at least offers a real-world analogy, he says. "However you want to deal with the semantics, I think grid computing, utility computing and cloud computing are all part of the same trend," Carr says.
Carr is not alone in thinking cloud is not the best word to describe today's transition to Web-based IT delivery models. For the enterprise, cloud computing might best be viewed as a series of "online business services," says IDC analyst Frank Gens.
什么是公有云？
Naturally, a public cloud is a service that anyone can tap into with a network connection and a credit card. "Public clouds are shared infrastructures with pay-as-you-go economics," explains Forrester analyst James Staten in an April report. "Public clouds are easily accessible, multitenant virtualized infrastructures that are managed via a self-service portal."
What is a private cloud?
A私有云attempts to mimic the delivery models of public cloud vendors but does so entirely within the firewall for the benefit of an enterprise's users. A private cloud would be highly virtualized, stringing together mass quantities of IT infrastructure into one or a few easily managed logical resource pools.
像公共云，私有云服务交付通常会通过自助服务和退款属性的Web界面完成。“私有云给你很多的云计算的好处，但它是私人拥有和管理，访问可能仅限于自己的企业或价值链中的一部分，” KLOECKNER说。“它确实驱动效率，它力的标准化和最佳实践。”
The largest enterprises are interested in private clouds because public clouds are not yet scalable and reliable enough to justify transferring all of their IT resources to cloud vendors, Carr says.
“很多，这是一个大规模的比赛，”卡尔说。“如果你是通用电气公司，你知道了一个庞大的你自己的公司内规模。而在这个阶段为你做聪明的做法可能是重建自己的内部IT围绕云架构，因为公共云是不成规模的在这一点上的可靠性和一切通用电气可能会说'我们现在要关门了我们所有的数据中心和移动到云中。”雷竞技电脑网站
Is cloud computing the same as software-as-a-service?
You might saysoftware-as-a-servicekicked off the whole push toward cloud computing by demonstrating that IT services could be easily made available over the Web. While SaaS vendors originally did not use the word cloud to describe their offerings, analysts now consider SaaS to be one of several subsets of the cloud computing market.
What types of services are available via the cloud computing model?
Public cloud services are breaking down into three broad categories: software-as-a-service, infrastructure-as-a-service, and platform-as-a-service. SaaS is well known and consists of software applications delivered over the Web. Infrastructure-as-a-service refers to remotely accessible server and storage capacity, while platform-as-a-service is a compute-and-software platform that lets developers build and deploy Web applications on a hosted infrastructure.
如何出售ors charge for these services?
SaaS vendors have long boasted of selling software on a pay-as-you-go, as-needed basis, preventing the kind of lock-in inherent in long-term licensing deals for on-premises software. Cloud infrastructure providers like Amazon are doing the same. For example, Amazon's Elastic Compute Cloud charges for per-hour usage of virtualized server capacity. A small Linux server costs 10 cents an hour, while the largest Windows server costs$ 1.20小时。
存储云类似的定价。Nirvanix的cloud storage platform has prices starting at 25 cents per gigabyte of storage each month, with additional charges for each upload and download.
What types of applications can run in the cloud?
Technically, you can put any application in the cloud. But that doesn't mean it's a good idea. For example, there's little reason to run a desktop disk defragmentation or systems analysis tool in the cloud, because you want the application sitting on the desktop, dedicated to the system with little to no latency, says Pund-IT analyst Charles King.
More importantly, regulatory and compliance concerns prevent enterprises from putting certain applications in the cloud, particularly those involving sensitive customer data.
IDC的调查显示，云的顶部用途为IT管理，协作，个人和商务应用，应用开发和部署，以及服务器和存储容量。
Can applications move from one cloud to another?
Yes, but that doesn't mean it will be easy. Services havepopped upto move applications from one cloud platform to another (such as from Amazon to GoGrid) and from internal data centers to the cloud. But going forward, cloud vendors will have to adopt standards-based technologies in order to ensure true interoperability, according to several industry groups. The recently released "Open Cloud Manifesto" supports interoperability of data and applications, while theOpen Cloud Consortiumis promoting open frameworks that will let clouds operated by different entities work seamlessly together. The goal is to move applications from one cloud to another without having to rewrite them.
如何传统的软件授权在云世界申请？
供应商和客户的一致好评与软件许可政策应如何适应云的问题挣扎。套装软件供应商要求的先期付款，并让客户支付的软件的能力，即使他们只使用25％或50％100％，发电说。该模型没有考虑的云服务的灵活性。
Oracle和IBM已经设计了解释他们的软件是如何授权给亚马逊的云，但大多数观察家似乎同意软件厂商做得还不够他们的许可适应云等效表。
金融服务公司ING，正在审查许多云服务，引牌作为其最大的担忧。“我还没有看到在软件许可，以匹配云服务提供商的灵活性，柔韧性的任何厂商，” ING的艾伦·博梅，该公司的高级副总裁兼IT战略和企业架构的负责人说。“这是一个艰难的一个，因为它是一种商业模式的变化。......这可能需要相当长的一段时间。”
What types of service-level agreements are cloud vendors providing?
Cloud vendors typically guarantee at least 99% uptime, but the ways in which that is calculated and enforced differ significantly. Amazon EC2 promises to make "commercially reasonable efforts" to ensure99.95% uptime。But uptime is calculated on a yearly basis, so if Amazon falls below that percentage for just a week or a month, there's no penalty or service credit.
GoGridpromises 100% uptime in its SLA. But as any lawyer points out, you have to pay attention to the legalese.GoGrid的的SLA包括此难以解释短语：“个人服务器将提供100％的正常运行时间作为GoGrid的网络通过GoGrid的监控系统内只监测由于在硬件已知GoGrid的问题和管理程序层提供单独的服务器构成故障和因此不故障。本SLA覆盖“。
律师大卫·斯尼德，谁最近谈到了云计算在SYS - 精读的云计算大会暨展览会在纽约市的计算法律问题，说亚马逊有显著的停机时间，但很难让客户获得服务信用。
“亚马逊将不会站在后面的产品，”斯尼德说。“现实情况是，他们不作任何保证。”
How can I make sure my data is safe?
Data safety in the cloud is not a trivial concern. Online storage vendors such asThe Linkupand无忧have lost data, and were unable to recover it for customers. Secondly, there is the danger that sensitive data could fall into the wrong hands. Before signing up with any cloud vendor, customers should demand information about data security practices, scrutinize SLAs, and make sure they have the ability to encrypt data both in transit and at rest.
我怎样才能确保我的应用程序有相同的性能水平运行，如果我有一个云供应商去？
Before choosing a cloud vendor, do your due diligence by examining the SLA to understand what it guarantees and what it doesn't, and scour through any publicly accessible availability data. Amazon, for example, maintains a "Service Health Dashboard" that shows current and historical uptime status of its various services.
总是会有一个云服务的一些网络延迟，可能使其慢于一个应用程序，在您的本地数据中心的运行。雷竞技电脑网站但第三方厂商的新作都在云的上方，以确保应用的可扩展建设的服务和良好表现，如RightScale。
通过and large, the performance hit related to latency "is pretty negligible these days," RightScale CTO Thorsten von Eicken. The largest enterprises are distributed throughout the country or world, he notes, so many users will experience a latency-caused performance hit whether an application is running in the cloud or in the corporate data center.
