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Cloud Computing - an Excerpt from Cloud Application Architectures

By Kathryn Barrett
April 9, 2009 | Comments: 4

george_reese.jpgThe following is an excerpt from Cloud Application Architectures, the latest book by George Reese. It has been adapted for the Web.

Cloud Computing

The hallmark of any buzzword is its ability to convey the appearance of meaning without conveying actual meaning. To many people, the term cloud computing has the feel of a buzzword.

It's used in many discordant contexts, often referencing apparently distinct things. In one conversation, people are talking about Google Gmail; in the next, they are talking about Amazon Elastic Compute Cloud (at least it has "cloud" in its name!).

But cloud computing is not a buzzword any more than the term the Web is. Cloud computing is the evolution of a variety of technologies that have come together to alter an organization's approach to building out an IT infrastructure. Like the Web a little over a decade ago, there is nothing fundamentally new in any of the technologies that make up cloud computing. Many of the technologies that made up the Web existed for decades when Netscape came along and made them accessible; similarly, most of the technologies that make up cloud computing have been around for ages. It just took Amazon to make them all accessible to the masses.

The purpose of this book is to empower developers of transactional web applications to leverage cloud infrastructure in the deployment of their applications. This book therefore focuses on the cloud as it relates to clouds such as Amazon EC2, more so than Google Gmail. Nevertheless, we should start things off by setting a common framework for the discussion of cloud computing.

The Cloud

The cloud is not simply the latest fashionable term for the Internet. Though the Internet is a necessary foundation for the cloud, the cloud is something more than the Internet. The cloud is where you go to use technology when you need it, for as long as you need it, and not a minute more. You do not install anything on your desktop, and you do not pay for the technology when you are not using it.

The cloud can be both software and infrastructure. It can be an application you access through the Web or a server that you provision exactly when you need it. Whether a service is software or hardware, the following is a simple test to determine whether that service is a cloud service:

If you can walk into any library or Internet cafe and sit down at any computer without preference for operating system or browser and access a service, that service is cloud-based.

I have defined three criteria I use in discussions on whether a particular service is a cloud service:

  • The service is accessible via a web browser (nonproprietary) or web services API.
  • Zero capital expenditure is necessary to get started.
  • You pay only for what you use as you use it.

I don't expect those three criteria to end the discussion, but they provide a solid basis for discussion and reflect how I view cloud services in this book.

If you don't like my boiled-down cloud computing definition, James Governor has an excellent blog entry on 15 Ways to Tell It's Not Cloud Computing.


As I mentioned earlier, cloud services break down into software services and infrastructure services. In terms of maturity, software in the cloud is much more evolved than hardware in the cloud.

Software as a Service (SaaS) is basically a term that refers to software in the cloud. Although not all SaaS systems are cloud systems, most of them are.

SaaS is a web-based software deployment model that makes the software available entirely through a web browser. As a user of SaaS software, you don't care where the software is hosted, what kind of operating system it uses, or whether it is written in PHP, Java, or .NET. And, above all else, you don't have to install a single piece of software anywhere.

Gmail, for example, is nothing more than an email program you use in a browser. It provides the same functionality as Apple Mail or Outlook, but without the fat client. Even if your domain does not receive email through Gmail, you can still use Gmail to access your mail.

SalesForce.com is another variant on SaaS. SalesForce.com is an enterprise customer relationship management (CRM) system that enables sales people to track their prospects and leads, see where those individuals sit in the organization's sales process, and manage the workflow of sales from first contact through completion of a sale and beyond. As with Gmail, you don't need any software to access SalesForce.com: point your web browser to the SalesForce.com website, sign up for an account, and get started.

SaaS systems have a few defining characteristics:

Availability via a web browser

SaaS software never requires the installation of software on your laptop or desktop. You access it through a web browser using open standards or a ubiquitous browser plug-in. Cloud computing and proprietary desktop software simply don't mix.

On-demand availability

You should not have to go through a sales process to gain access to SaaS-based software. Once you have access, you should be able to go back into the software any time, from anywhere.

Payment terms based on usage

SaaS does not need any infrastructure investment or fancy setup, so you should not have to pay any massive setup fees. You should simply pay for the parts of the service you use as you use them. When you no longer need those services, you simply stop paying.

Minimal IT demands

If you don't have any servers to buy or any network to build out, why do you need an IT infrastructure? While SaaS systems may require some minimal technical knowledge for their configuration (such as DNS management for Google Apps), this knowledge lays within the realm of the power user and not the seasoned IT administrator.

One feature of some SaaS deployments that I have intentionally omitted is multitenancy. A number of SaaS vendors boast about their multitenancy capabilities--some even imply that multitenancy is a requirement of any SaaS system.

A multitenant application is server-based software that supports the deployment of multiple clients in a single software instance. This capability has obvious advantages for the SaaS vendor that, in some form, trickle down to the end user:

  • Support for more clients on fewer hardware components
  • Quicker and simpler rollouts of application updates and security patches
  • Architecture that is generally more sound

The ultimate benefit to the end user comes indirectly in the form of lower service fees, quicker access to new functionality, and (sometimes) quicker protection against security holes. However, because a core principle of cloud computing is a lack of concern for the underlying architecture of the applications you are using, the importance of multitenancy is diminished when looking at things from that perspective.

As we discuss in the next section, virtualization technologies essentially render the architectural advantages of multitenancy moot.


In general, hardware in the cloud is conceptually harder for people to accept than software in the cloud. Hardware is something you can touch: you own it; you don't license it. If your server catches on fire, that disaster matters to you. It's hard for many people to imagine giving up the ability to touch and own their hardware.

With hardware in the cloud, you request a new "server" when you need it. It is ready as quickly as 10 minutes after your request. When you are done with it, you release it and it disappears back into the cloud. You have no idea what physical server your cloud-based server is running, and you probably don't even know its specific geographic location.

The Barrier of Old Expectations

The hardest part for me as a vendor of cloud-based computing services is answering the question, "Where are our servers?" The real answer is, inevitably, "I don't know--somewhere on the East Coast of the U.S. or Western Europe," which makes some customers very uncomfortable. This lack of knowledge of your servers' location, however, provides an interesting physical security benefit, as it becomes nearly impossible for a motivated attacker to use a physical attack vector to compromise your systems.

The advantages of a cloud infrastructure

Think about all of the things you have to worry about when you own and operate your own servers:

Running out of capacity?

Capacity planning is always important. When you own your own hardware, however, you have two problems that the cloud simplifies for you: what happens when you are wrong (either overoptimistic or pessimistic), and what happens if you don't have the expansion capital when the time comes to buy new hardware. When you manage your own infrastructure, you have to cough up a lot of cash for every new Storage Area Network (SAN) or every new server you buy. You also have a significant lead time from the moment you decide to make a purchase to getting it through the procurement process, to taking delivery, and finally to having the system racked, installed, and tested.

What happens when there is a problem?

Sure, any good server has redundancies in place to survive typical hardware problems. Even if you have an extra hard drive on hand when one of the drives in your RAID array fails, someone has to remove the old drive from the server, manage the RMA,[1] and put the new drive into the server. That takes time and skill, and it all needs to happen in a timely fashion to prevent a complete failure of the server.

[1] Return merchandise authorization. When you need to return a defective part, you generally have to go through some vendor process for returning that part and obtaining a replacement.

What happens when there is a disaster?

If an entire server goes down, unless you are in a high-availability infrastructure, you have a disaster on your hands and your team needs to rush to address the situation. Hopefully, you have solid backups in place and a strong disaster recovery plan to get things operational ASAP. This process is almost certainly manual.
Don't need that server anymore?
Perhaps your capacity needs are not what they used to be, or perhaps the time has come to decommission a fully depreciated server. What do you do with that old server? Even if you give it away, someone has to take the time to do something with that server. And if the server is not fully depreciated, you are incurring company expenses against a machine that is not doing anything for your business.

What about real estate and electricity?

When you run your own infrastructure (or even if you have a rack at an ISP), you may be paying for real estate and electricity that are largely unused. That's a very ungreen thing, and it is a huge waste of money.

None of these issues are concerns with a proper cloud infrastructure:

  • You add capacity into a cloud infrastructure the minute you need it, and not a moment sooner. You don't have any capital expense associated with the allocation, so you don't have to worry about the timing of capacity needs with budget needs. Finally, you can be up and running with new capacity in minutes, and thus look good even when you get caught with your pants down.
  • You don't worry about any of the underlying hardware, ever. You may never even know if the physical server you have been running on fails completely. And, with the right tools, you can automatically recover from the most significant disasters while your team is asleep.
  • When you no longer need the same capacity or you need to move to a different virtual hardware configuration, you simply deprovision your server. You do not need to dispose of the asset or worry about its environmental impact.
  • You don't have to pay for a lot of real estate and electricity you never use. Because you are using a fractional portion of a much beefier piece of hardware than you need, you are maximizing the efficiency of the physical space required to support your computing needs. Furthermore, you are not paying for an entire rack of servers with mostly idle CPU cycles consuming electricity.

Hardware virtualization

Hardware virtualization is the enabling technology behind many of the cloud infrastructure vendors offerings, including Amazon Web Services (AWS).[2] If you own a Mac and run Windows or Linux inside Parallels or Fusion, you are using a similar virtualization technology to those that support cloud computing. Through virtualization, an IT admin can partition a single physical server into any number of virtual servers running their own operating systems in their allocated memory, CPU, and disk footprints. Some virtualization technologies even enable you to move one running instance of a virtual server from one physical server to another. From the perspective of any user or application on the virtual server, no indication exists to suggest the server is not a real, physical server.

[2] Other approaches to cloud infrastructure exist, including physical hardware on-demand through companies such as AppNexus and NewClouds. In addition, providers such as GoGrid (summarized in Appendix B) offer hybrid solutions.

A number of virtualization technologies on the market take different approaches to the problem of virtualization. The Amazon solution is an extension of the popular open source virtualization system called Xen. Xen provides a hypervisor layer on which one or more guest operating systems operate. The hypervisor creates a hardware abstraction that enables the operating systems to share the resources of the physical server without being able to directly access those resources or their use by another guest operating system.

A common knock against virtualization--especially for those who have experienced it in desktop software--is that virtualized systems take a significant performance penalty. This attack on virtualization generally is not relevant in the cloud world for a few reasons:

  • The degraded performance of your cloud vendor's hardware is probably better than the optimal performance of your commodity server.
  • Enterprise virtualization technologies such as Xen and VMware use paravirtualization as well as the hardware-assisted virtualization capabilities of a variety of CPU manufacturers to achieve near-native performance.

Cloud storage

Abstracting your hardware in the cloud is not simply about replacing servers with virtualization. It's also about replacing your physical storage systems.

Cloud storage enables you to "throw" data into the cloud and without worrying about how it is stored or backing it up. When you need it again, you simply reach into the cloud and grab it. You don't know how it is stored, where it is stored, or what has happened to all the pieces of hardware between the time you put it in the cloud and the time you retrieved it.

As with the other elements of cloud computing, there are a number of approaches to cloud storage on the market. In general, they involve breaking your data into small chunks and storing that data across multiple servers with fancy checksums so that the data can be retrieved rapidly—no matter what has happened in the meantime to the storage devices that comprise the cloud.

I have seen a number of people as they get started with the cloud attempt to leverage cloud storage as if it were some kind of network storage device. Operationally, cloud storage and traditional network storage serve very different purposes. Cloud storage tends to be much slower with a higher degree of structure, which often renders it impractical for runtime storage for an application, regardless of whether that application is running in the cloud or somewhere else.

Cloud storage is not, generally speaking, appropriate for the operational needs of transactional cloud-based software. Later, we discuss in more detail the role of cloud storage in transaction application management. For now, think of cloud storage as a tape backup system in which you never have to manage any tapes.

Note: Amazon recently introduced a new offering called Amazon CloudFront, which leverages Amazon S3 as a content distribution network. The idea behind Amazon CloudFront is to replicate your cloud content to the edges of the network. While Amazon S3 cloud storage may not be appropriate for the operational needs of many transactional web applications, CloudFront will likely prove to be a critical component to the fast, worldwide distribution of static content.

Cloud Application Architectures

We could spend a lot of precious paper discussing Software as a Service or virtualization technologies (did you know that you can mix and match at least five kinds of virtualization?), but the focus of this book is how you write an application so that it can best take advantage of the cloud.

Grid Computing

Grid computing is the easiest application architecture to migrate into the cloud. A grid computing application is processor-intensive software that breaks up its processing into small chunks that can then be processed in isolation.

If you have used SETI@home, you have participated in grid computing. SETI (the Search for Extra-Terrestrial Intelligence) has radio telescopes that are constantly listening to activity in space. They collect volumes of data that subsequently need to be processed to search for a nonnatural signal that might represent attempts at communication by another civilization. It would take so long for one computer to process all of that data that we might as well wait until we can travel to the stars. But many computers using only their spare CPU cycles can tackle the problem extraordinarily quickly.

These computers running SETI@home--perhaps including your desktop--form the grid. When they have extra cycles, they query the SETI servers for data sets. They process the data sets and submit the results back to SETI. Your results are double-checked against processing by other participants, and interesting results are further checked.[3]

[3] For more information on SETI@home and the SETI project, pick up a copy of O'Reilly's Beyond Contact.

Back in 1999, SETI elected to use the spare cycles of regular consumers' desktop computers for its data processing. Commercial and government systems used to network a number of supercomputers together to perform the same calculations. More recently, server farms were created for grid computing tasks such as video rendering. Both supercomputers and server farms are very expensive, capital-intensive approaches to the problem of grid computing.

The cloud makes it cheap and easy to build a grid computing application. When you have data that needs to be processed, you simply bring up a server to process that data. Afterward, that server can either shut down or pull another data set to process.

Figure 1-1 illustrates the process flow of a grid computing application. First, a server or server cluster receives data that requires processing. It then submits that job to a message queue (1). Other servers--often called workers (or, in the case of SETI@home, other desktops)--watch the message queue (2) and wait for new data sets to appear. When a data set appears, the first computer to see it processes it and then sends the results back into the message queue (3). The two components can operate independently of each other, and one can even be running when no computer is running the other.

Figure 1-1. The grid application architecture separates the core application from its data processing nodes


Cloud computing comes to the rescue here because you do not need to own any servers when you have no data to process. You can then scale the number of servers to support the number of data sets that are coming into your application. In other words, instead of having idle computers process data as it comes in, you have servers turn themselves on as the rate of incoming data increases, and turn themselves off as the data rate decreases.

Because grid computing is currently limited to a small market (scientific, financial, and other large-scale data crunchers), this book doesn't focus on its particular needs. However, many of the principles in this book are still applicable.

Transactional Computing

Transactional computing makes up the bulk of business software and is the focus of this book. A transaction system is one in which one or more pieces of incoming data are processed together as a single transaction and establish relationships with other data already in the system. The core of a transactional system is generally a relational database that manages the relations among all of the data that make up the system.

Figure 1-2 shows the logical layout of a high-availability transactional system. Under this kind of architecture, an application server typically models the data stored in the database and presents it through a web-based user interface that enables a person to interact with the data. Most of the websites and web applications that you use every day are some form of transactional system. For high availability, all of these components may form a cluster, and the presentation/business logic tier can hide behind a load balancer.

Figure 1-2. A transactional application separates an application into presentation, business logic, and data storage


Deploying a transactional system in the cloud is a little more complex and less obvious than deploying a grid system. Whereas nodes in a grid system are designed to be short-lived, nodes in a transactional system must be long-lived.

A key challenge for any system requiring long-lived nodes in a cloud infrastructure is the basic fact that the mean time between failures (MTBF) of a virtual server is necessarily less than that for the underlying hardware. An admittedly gross oversimplification of the problem shows that if you have two physical servers with a three-year MTBF, you will be less likely to experience an outage across the entire system than you would be with a single physical server running two virtual nodes. The number of physical nodes basically governs the MTBF, and since there are fewer physical nodes, there is a higher MTBF for any given node in your cloud-based transactional system.

The cloud, however, provides a number of avenues that not only help mitigate the lower failure rate of individual nodes, but also potentially increase the overall MTBF for your transactional system. In this book, we cover the tricks that will enable you to achieve levels of availability that otherwise might not be possible under your budget while still maintaining transactional integrity of your cloud applications.

The Value of Cloud Computing

How far can you take all of this?

If you can deploy all of your custom-built software systems on cloud hardware and leverage SaaS systems for your packaged software, you might be able to achieve an all-cloud IT infrastructure. Table 1-1 lists the components of the typical small- or medium-sized business.

Table 1-1. The old IT infrastructure versus the cloud


The potential impact of the cloud is significant. For some organizations—particularly small- to medium-sized businesses—it makes it possible to never again purchase a server or own any software licenses. In other words, all of these worries diminish greatly or disappear altogether:

  • Am I current on all my software licenses? SaaS systems and software with cloud-friendly licensing simply charge your credit card for what you use.
  • When do I schedule my next software upgrade? SaaS vendors perform the upgrades for you; you rarely even know what version you are using.
  • What do I do when a piece of hardware fails at 3 a.m.? Cloud infrastructure management tools are capable of automating even the most traumatic disaster recovery policies.
  • How do I manage my technology assets? When you are in the cloud, you have fewer technology assets (computers, printers, etc.) to manage and track.
  • What do I do with my old hardware? You don't own the hardware, so you don't have to dispose of it.
  • How do I manage the depreciation of my IT assets? Your costs are based on usage and thus don't involve depreciable expenses.
  • When can I afford to add capacity to my infrastructure? In the cloud, you can add capacity discretely as the business needs it.

SaaS vendors (whom I've included as part of cloud computing) can run all their services in a hardware cloud provided by another vendor, and therefore offer a robust cloud infrastructure to their customers without owning their own hardware. In fact, my own business runs that way.

Options for an IT Infrastructure

The cloud competes against two approaches to IT:

  • Internal IT infrastructure and support

  • Outsourcing to managed services

If you own the boxes, you have an internally managed IT infrastructure—even if they are sitting in a rack in someone else's data center. For you, the key potential benefit of cloud computing (certainly financially) is the lack of capital investment required to leverage it.

Internal IT infrastructure and support is one in which you own the boxes and pay people—whether staff or contract employees—to maintain those boxes. When a box fails, you incur that cost, and you have no replacement absent a cold spare that you own.

Managed services outsourcing has similar benefits to the cloud in that you pay a fixed fee for someone else to own your servers and make sure they stay up. If a server goes down, it is the managed services company who has to worry about replacing it immediately (or within whatever terms have been defined in your service-level agreement). They provide the expertise to make sure the servers are fixed with the proper operating system patches and manage the network infrastructure in which the servers operate.

Table 1-2 provides a comparison between internal IT, managed services, and cloud-based IT with respect to various facets of IT infrastructure development.

Table 1-2. A comparison of IT infrastructure options


[4] From a financial perspective, the difference between coughing up cash today and borrowing it from a bank is inconsequential. Either way, spending $40K costs you money. If you borrow it, you pay interest. If you take it out of your bank account, you lose the opportunity to do something else with it (cost of capital).

The one obvious fact that should jump out of this chart is that building an IT infrastructure from scratch no longer makes any sense. The only companies that should have an internal IT are organizations with a significant preexisting investment in internal IT or with regulatory requirements that prevent data storage in third-party environments.

Everyone else should be using a managed services provider or the cloud.

The Economics

Perhaps the biggest benefit of cloud computing over building out your own IT infrastructure has nothing to do with technology—it's financial. The "pay for what you use" model of cloud computing is significantly cheaper for a company than the "pay for everything up front" model of internal IT.

Capital costs

The primary financial problem with an internally based IT infrastructure is the capital cost. A capital cost is cash you pay for assets prior to their entering into operations. If you buy a server, that purchase is a capital cost because you pay for it all up front, and then you realize its benefits (in other words, you use it) over the course of 2-3 years.

Let's look at the example of a $5,000 computer that costs $2,000 to set up. The $5,000 is a capital cost and the $2,000 is a one-time expense. From an accounting perspective, the $5,000 cost is just a "funny money" transaction, in that $5,000 is moved from one asset account (your bank account) into another asset account (your fixed assets account). The $2,000, on the other hand, is a real expense that offsets your profits.

The server is what is called a depreciable asset. As it is used, the server is depreciated in accordance with how much it has been used. In other words, the server's value to the company is reduced each month it is in use until it is worth nothing and removed from service. Each reduction in value is considered an expense that offsets the company's profits.

Finance managers hate capital costs for a variety of reasons. In fact, they hate any expenses that are not tied directly to the current operation of the company. The core rationale for this dislike is that you are losing cash today for a benefit that you will receive slowly over time (technically, over the course of the depreciation of the server). Any business owner or executive wants to focus the organization's cash on things that benefit them today. This concern is most acute with the small- and medium-sized business that may not have an easy time walking into the bank and asking for a loan.

The key problem with this delayed realization of value is that money costs money. A company will often fund their operational costs through revenues and pay for capital expenses through loans. If you can grow the company faster than the cost of money, you win. If you cannot grow that rapidly or—worse—you cannot get access to credit, the capital expenses become a significant drain on the organization.

Cost comparison

Managed services infrastructures and the cloud are so attractive to companies because they largely eliminate capital investment and other up-front costs. The cloud has the added advantage of tying your costs to exactly what you are using, meaning that you can often connect IT costs to revenue instead of treating them as overhead.

Table 1-3 compares the costs of setting up an infrastructure to support a single "moderately high availability" transactional web application with a load balancer, two application servers, and two database servers. I took typical costs at the time of writing, October 2008.

Table 1-3. Comparing the cost of different IT infrastructures


Table 1-3 makes the following assumptions:

  • The use of fairly standard 1u server systems, such as a Dell 2950 and the high-end Amazon instances.
  • The use of a hardware load balancer in the internal IT and managed services configuration and a software load balancer in the cloud.
  • No significant data storage or bandwidth needs (different bandwidth or storage needs can have a significant impact on this calculation).
  • The low end of the cost spectrum for each of the options (in particular, some managed services providers will charge up to three times the costs listed in the table for the same infrastructure).
  • Net costs denominated in today's dollars (in other words, don't worry about inflation).
  • A cost of capital of 10% (cost of capital is what you could have done with all of the up-front cash instead of sinking it into a server and setup fees--basically the money's interest rate plus opportunity costs).
  • The use of third-party cloud management tools such as enStratus or RightScale, incorporated into the cloud costs.
  • Staff costs representing a fraction of an individual (this isolated infrastructure does not demand a full-time employee under any model).

Perhaps the most controversial element of this analysis is what might appear to be an "apples versus oranges" comparison on the load balancer costs. The reality is that this architecture doesn't really require a hardware load balancer except for extremely high-volume websites. So you likely could get away with a software load balancer in all three options.

A software load balancer, however, is very problematic in both the internal IT and managed services infrastructures for a couple of reasons:

  • A normal server is much more likely to fail than a hardware load balancer. Because it is much harder to replace a server in the internal IT and managed services scenarios, the loss of that software load balancer is simply unacceptable in those two scenarios, whereas it would go unnoticed in the cloud scenario.
  • If you are investing in actual hardware, you may want a load balancer that will grow with your IT needs. A hardware load balancer is much more capable of doing that than a software load balancer. In the cloud, however, you can cheaply add dedicated software load balancers, so it becomes a nonissue.

In addition, some cloud providers (GoGrid, for example) include free hardware load balancing, which makes the entire software versus hardware discussion moot. Furthermore, Amazon is scheduled to offer its own load-balancing solution at some point in 2009. Nevertheless, if you don't buy into my rationale for comparing the hardware load balancers against the software load balancers, here is the comparison using all software load balancers: $134K for internal IT, $92K for managed services, and $106K for a cloud environment.

The bottom line

If we exclude sunk costs, the right managed services option and cloud computing are always financially more attractive than managing your own IT. Across all financial metrics—capital requirements, total cost of ownership, complexity of costs—internal IT is always the odd man out.

As your infrastructure becomes more complex, determining whether a managed services infrastructure, a mixed infrastructure, or a cloud infrastructure makes more economic sense becomes significantly more complex.

If you have an application that you know has to be available 24/7/365, and even 1 minute of downtime in a year is entirely unacceptable, you almost certainly want to opt for a managed services environment and not concern yourself too much with the cost differences (they may even favor the managed services provider in that scenario).

On the other hand, if you want to get high-availability on the cheap, and 99.995% is good enough, you can't beat the cloud.

Urquhart on Barriers to Exit

In November 2008, James Urquhart and I engaged in a Twitter discussion relating to the total cost of ownership of cloud computing (James is a market manager for the Data Center 3.0 strategy at Cisco Systems and member of the CNET blog network). What we realized is that I was looking at the problem from the perspective of starting with a clean slate; James was looking at the problem from the reality of massive existing investments in IT. What follows is a summary of our discussion that James has kindly put together for this book.

While it is easy to get enthusiastic about the economics of the cloud in "green-field" comparisons, most modern medium-to-large enterprises have made a significant investment in IT infrastructure that must be factored into the cost of moving to the cloud.

These organizations already own the racks, cooling, and power infrastructure to support new applications, and will not incur those capital costs anew. Therefore, the cost of installing and operating additional servers will be significantly less than in the examples.

In this case, these investments often tip the balance, and it becomes much cheaper to use existing infrastructure (though with some automation) to deliver relatively stable capacity loads. This existing investment in infrastructure therefore acts almost as a "barrier-to-exit" for such enterprises considering a move to the cloud.

Of course, there are certain classes of applications that even a large enterprise will find more cost effective to run in the cloud. These include:

  • Applications with widely varying loads, for which peak capacity is hard to predict, and for which purchasing for peak load would be inefficient most of the time anyway.

  • Applications with occasional or periodic load spikes, such as tax processing applications or retail systems hit hard prior to the holidays. The cloud can provide excess capacity in this case, through a technique called "cloudbursting."

  • New applications of the type described in this book that would require additional data center space or infrastructure investment, such as new cooling or power systems.

It seems to me highly ironic—and perhaps somewhat unique—that certain aspects of the cloud computing market will be blazed not by organizations with multiple data centers and thousands upon thousands of servers, but by the small business that used to own a few servers in a server hotel somewhere that finally shut them down and turned to Amazon. How cool is that?

CloudAppArch.jpgIf you like what you've read here and would like to read more, get the book: Cloud Application Architectures by George Reese.

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Italics making eyes bleed!

We're a startup looking for cheap hosting. In order of most expensive to least our options go like this:
1) cloud
2) dedicated hosting company with multiple data centres.
3) two small hosting companies with one data centre each.

Obviously, we've got to be careful with replication on the last option as it's done over the public internet.

The cloud option was far more expensive than the other two. (We looked at Amazon, Google and a couple of smaller players.)

Well, many people have talked about what is, what isn’t and benefits of cloud computing, but I think it’s time to really build an infrastructure based on the cloud. This book can answer many questions about the design and implementation of such systems for today’s enterprises needs.

I only hope an O'Reilly store near to my home :(

Well written and simple to follow.
I needed to get an idea about the hardware and this was just what I needed, thanks.

Cloud computing, the dynamic data center.

Cloud computing helps to increase the speed at which applications are deployed, helping to increase the pace of innovated networked computing. Service deployed applications; Cloud computing can be provided using an enterprise data center’s own servers, or it can be provided by a cloud provider that takes all of the capital risk of owning the infrastructure.

Cloud computing incorporates virtualization, data and application on-demand deployment, internet delivery of services, and open source software. Virtualization enables a dynamic data center where servers provide resources that are utilized as needed with resources changing dynamically in order to meet the needed workload.

The combination of virtual machines and virtual appliances used for server deployment objects is one of the key features of cloud computing. Additionally, company’s can merge a storage cloud that provides a virtualized storage platform and is managed through an API, or Web-based interfaces for file management, and application data deployments.

Layered Service providers offering pay-by-use cloud computing solutions can be adjacent to company’s equipment leases. Public clouds are run by third party service providers and applications from different customers are likely to be mixed together on the cloud’s servers, storage systems, and networks. Private clouds are built for the exclusive use of one client, providing the utmost control over data, security, and quality of service. Private clouds can also be built and managed by a company’s own IT administrator. Hybrid clouds combine both public and private cloud models which may be used to handle planned workload spikes, or storage clouds configuration. Dedicated audits for security policies are a must.

The benefits of deploying applications using cloud computing include reducing run time and response time, minimizing the purchasing and deployment of physical infrastructure. Considerations for Energy efficiency, flexibility, simplified systems administration, pricing based on consumption, and most of all limiting the footprint of the data center. Virtualized solutions: http://www.shopricom.com


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