Cloud Computing Models: Public VS Private VS Community VS Hybrid

Cloud computing is a unique computing type that provides access to the appropriate network and on-demand set of configurable computing resources such as networks, servers, storage, applications and services. These computing resources can be provisioned and released quickly and without much effort, management and interaction by the cloud hosting services provider.

The term “cloud” is commonly used to represent the provisioning of computing resources through Internet.

Types of Cloud Computing Model

There are four different types of cloud computing model or cloud infrastructure. These models are distinguished based on the ownership of the cloud infrastructure. Following are the four types of cloud models:

  • Public Cloud Infrastructure
  • Private Cloud Infrastructure
  • Community Cloud Infrastructure
  • Hybrid Cloud Infrastructure

Let’s have a look at the cloud computing models definitions and its advantages and disadvantages.

Definitions, Advantages and Disadvantages of Cloud Models

Definition of Public Cloud

It is a type of cloud in which the infrastructure and logical resources that are part of cloud environment are available to the public via Internet. This is usually owned by a provider who manages the infrastructure and services offered.


  • Increased scalability and unlimited resources;
  • Resource efficiency via pay-per-use model;
  • Time and cost savings.


  • Sharing of Infrastructure with multiple organizations;
  • Lacks of transparency, as the clients are unaware about the same resources and storage being used by other multiple services.

Definition of Private Cloud

This is a computing model where a cloud is privately implemented within the corporate firewall and is under the control of the organizations IT department.


  • Compliance with internal policies;
  • Ease of collaborative work between distributed sites;
  • Complete control over the resources.


  • High cost material;
  • Hired infrastructure unit;
  • Return on Investment (ROI) is slow.

Definition of Community Cloud

This computing model is happen when two or more organizations form a partnership to implement a cloud infrastructure with a similar goal-oriented and a common security framework and privacy.


  • Compliance with internal policies;
  • Cost Reduction by sharing of infrastructure and resources;
  • Return on Investment (ROI) is fast.


  • Managed by organization or third party;
  • Hired infrastructure unit.
  • Definition of Hybrid Cloud

The hybrid cloud is a broad term involving a joint use of multiple cloud models or infrastructures any of the above three types, which are kept as separate entities, however which in turn are associated by standardized or proprietary technology, offering data and application portability.

Advantages and disadvantages of hybrid cloud are same as those cloud models used to form a hybrid cloud hosting environment.



What is bandwidth on demand?

Although the service bandwidth on demand is something that does not exist in all industrialized countries, is giving successful in some sites could be something spread everywhere within some time. The bandwidth on demand offers mobile broadband with a prepaid basis (Mobile Internet). A person registered to this service pay for one day of use, for a week or a month living with access to the Internet. This service provides temporary connectivity to people who do not want or do not need to have constant access to the network. Can also be used as an adjunct to other established service, which can be used when the standard Internet connection does not work for some reason. This instant access to the Internet from almost anywhere, it is through phone towers.

This type of service is usually more expensive than other delivery plans, but also quite comfortable in many circumstances. With this service you can have anytime access to the Internet while we’re on a bus, in the park, on the beach or anywhere where there is a telephone service, and you do not have a fixed contract with a company. To access this service, a user must first purchase a card for PC or USB device that can handle the protocols between the computer and the provider of the mobile bandwidth. If you choose another provider, card or device to that service is required.

Once the device is inserted into the port or slot, just type the credentials and an advance payment for the period of time needed. Normally, the minimum time required is a full day, where prices vary by provider and location. There are certain limits on the amount of data that can be downloaded without any additional charges to the contracted time. If you go past the limit, it will start charging for downloaded megabytes, in the same way that happens when you pass the time in a telephony service. This prevents the network from collapsing by a massive discharge use. In most cases, the limit is sufficient.

Most of all mobile network companies offer Mobile internet services (EDGE, 2G and 3G on Mobile). In many cases, you need to have a contract with a specific company to qualify for the service. Speeds vary significantly depending on the provider, the network traffic, the quality of the connection and the user’s location at any given time. Before deciding on a mobile provider, be sure to check the coverage maps and networks available in the area. Good coverage is important if we are going to move a lot of back and forth. Bandwidth on Demand provides access to a secure connection in emergencies or when no other form of connectivity available. It is also a good choice to travel both nationally and internationally.


What is an Apache ?

There is no Indian tribe or military helicopter, but something related to the world of Internet, especially the Web pages. Apache is recognized as one of the most popular web servers worldwide. Originally, it was designed for Unix environments but then it was been integrated with other operating systems such as Windows. The term “apache” is used to describe earlier versions of the software. The Apache Web server provides a wide range of functions such as HTTP server. Includes CGI, SSL, and virtual domains. It also supports the integration of external modules to be more extensible. Best of all it’s free, and is distributed by a foundation that promotes itself open source and free technology.

Even being one of the server that is more popular according to many studies that have been done, it is sometimes a little confusing especially for those who are not too close to the world of Unix and Linux. Instead of graphical interfaces and Windows registry as most software packages that are installed, the Apache server is usually based on simple text files to your settings. To be more exact, Apache uses a three text files to manage configuration data. These files are almost always found in the directory ./conf and are designed for system administrators for edit. The files are httpd.conf for general configuration settings for srm.conf resources and access.conf file for security settings.

When Apache starts up for the first time, these files are processed in the order they are described. Originally, Apache installation default entries included in each of the three files. However, in the latest versions of Apache, the default installation has changed. Now httpd.conf is treated as the master file and contains all configurations. Anyway, the other two files still exist in the system, but do not contain settings (only some comments). Like many Unix-like programs, Apache must be restarted for the new settings to take effect.

What’s in a httpd.conf?

Traditionally, this configuration file usually contained as the server name and port number. The term “httpd” means the HTTP daemon. This may not make much sense on a Windows platform, but Linux and Unix can be compared to Windows services. This file contains more entries, but many of these changes are optional. Input may be more useful. ServerAdmin – allows the machine operator to configure the e-mail that appears in error pages in the browser of the user. This allows users to contact someone if the website has problems.

The access and security settings have their setup to install Apache. It is recommended for Apache administrators to change security settings and resources from httpd.conf practice. Administrators of older versions can simply cut and paste the entries from the other files mentioned above, and put it in httpd.conf. If for some reason you want to delete srm.conf and access.conf files, put two entries in the httpd.conf file, which would be as follows:

AccessConfig / dev / null
ResourceConfig / dev / null

The group of .conf files support many of the Apache settings, but not all. Other important mechanisms for managing an Apache Web server include other files, such as log, .htaccess, etc.


Discover How To Improve The Performance of SSDs to 300%

A team of researchers from Japan Chuo University has made an important discovery, through it would be possible to improve the performance of the SSDs up to 300%, further reducing consumption by 60%.

Sounds good, right? So it is best that this milestone is that, its implementation would occur through a firmware upgrade, allowing even relatively old SSDs can get to benefit from this discovery. That said I do not expect more, sure you are dying to know how this improvement can be done as more as possible, so I offer an explanation as simple as possible.

Today SSDs cannot directly overwrite data in a memory area, which means that the new data should be written in a different area until the previous is completely invalidated, that is eliminated. This topic TRIM plays an important role within the SSD, as it tells the operating system data blocks that are no longer used and can be deleted, but does not prevent performance degradation that will be produced gradually with the simple use of SSD. Yes, you have right, occurs a kind of fragmentation, which is negative not only for the performance of the SSD, but can also reduce the life. Well, with these remarks in mind we can better understand the discovery.

The key is a middleware (software that helps an application to interact with other applications) as amended which controls the way in which you write and store data on the drive, using what is known as “logical block address scrambler”. This “logical block address encoder” prevents data from being written to a new area, enabling a kind of overwriting and placing the data in a block can be erased in the next step. The above means fewer pages data on the disk and reduces the cycles of write-erase up to 55%, increasing the lifespan of the SSD. But this is not the only benefit, as well a performance boost of up to 300% and a reduction would be achieved consumption of 60%. If we consider an SSD with a speed of 500 MB / s would be talking about an impressive increase, and we would go up to 1.5 GB / s and, as anticipated, all thanks to a simple update.



How does a SMTP server work ?

Whenever you send an email, your mail client interacts with the SMTP server to handle shipping. The SMTP server on your computer can have conversations with other servers SMTP to deliver emails. Assume that we want to send an email. My email id is Jordan and I have my account I want to send an email to and am using a client that is installed on my computer which is Outlook Express. When I set my mind in , told Outlook Express the name of the mail server – When I create a post and give it to the submit button, what happens is the following:

1 – Outlook Express connects to the SMTP server hosted in using port 25.

2 – Outlook Express has a conversation with the SMTP server telling the destination address and the address of the sending mail, as well as the content of the email.

3 – The SMTP server takes the part of the address in the “to” ( and divided into two parts: the name of the recipient (yourname) and the domain name ( If the address in the “to” have been another user, the server simply had delivered the message to the POP3 server (using a program called delivery agent). Being the recipient in another domain, SMTP needs to communicate with that domain.

4 – The SMTP server has a conversation with a domain name server, or DNS. Tells about “Can you give me the IP address of the SMTP Server “. The DNS server replies with one or more IP addresses associated with the SMTP server

5 – The SMTP server connects to an SMTP server using port 25. It has the same conversation in plain text that the client had with the SMTP server, and delivers the message to the server. The server recognizes the domain name which delivers the message to the POP3 server, which puts the message in the inbox.

If for some reason, the SMTP server cannot connect to the mail server of, then the message is queued. The server on many machines, using a program called sendmail for delivery. The sendmail program will try to periodically resend the messages you have in your queue. For example, you can try to resend the mail every 10 minutes. After four hours, usually sends you an email saying that there is something wrong. After five days, most sendmail configurations desist from sending email and we will resend them to us.

An SMTP server understands simple commands in plain text, and the most common are:

  • HELO – Discovered
  • EHLO – Discovered and request extended mode
  • MAIL FROM – Specifies the sender
  • TCPT TO – Specifies the recipient
  • DATA – Specifies the message body
  • RSET – Reset
  • QUIT – Logs
  • HELP – Help with Commands
  • VRFY – Verify an address
  • VERB – In verbal mode

In the next part of the article, we will see how the POP3 server works.