Skip to main content

Straight Talk: What is the cloud?

The cloud offers solutions for every data and computing service possible. This series dives into the question regarding whether cloud computing can be used for data backup and, if so, where? The goal is to understand the cloud as it relates to data storage, then to understand backup requirements and finally to identify where the cloud will and will not work for data backup.

In the first chapter, we define the three types of cloud: private, public and hybrid. We categorise these by the requirements each can meet. This chapter allows you to understand the key market definitions for the cloud as it relates to data storage.

The National Institute of Standards and Technology (NIST) defines cloud computing as "a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources — for example, networks, servers, storage, applications, and services — that can be rapidly provisioned and released with minimal management effort or service provider interaction." At the highest level, the cloud provides the means through which computing resources can be delivered as a service whenever and wherever you need them.

The cloud complements and can replace corporate-owned and managed resources. With the cloud, IT departments can increase or decrease computing resources without purchasing onsite equipment and software, training employees to support the infrastructure, or building out more data centres.

Read more: Introduction to the cloud for data backup and disaster recovery

The model that cloud providers employ in charging for cloud services is similar to the model that utilities employ for providing services to your home. For example, when electricity is used, you are charged for the usage by kilowatt hour. In a similar way, IT departments and users are charged for cloud services based on usage; however, in this case, usage is metered by application, server, storage, or network resources consumed.

Before discussing how backup and disaster recovery can leverage the cloud, we will first look at the various cloud configurations. Clouds are typically defined according to three classifications:

  • Private
  • Public
  • Hybrid

Private cloud

The private cloud most often refers to an external private cloud, which allows IT departments to maintain dedicated resources while also being able to outsource some or all of their entire infrastructure. Instead of your IT department owning, amortising and operating all of its own computing resources, it outsources some or all of these resources to a third-party hosting provider while maintaining the performance and security of its own dedicated systems. An organisation may utilise a third-party hosting facility for any of the following reasons:

  • Capacity constraints in its current data centre
  • Need for a separate facility for a small amount of equipment
  • Short-term duration of a data centre project
  • Capital expense preservation

Private cloud use cases:

The benefits of the private cloud include the following:

  • High levels of security, data integrity, auditability, and control since the data is on a dedicated system
  • High levels of performance
  • High levels of reliability and uptime
  • Reduced IT staff
  • Possible elimination of up-front capital equipment costs
  • Payment by usage
  • Ability to dial-up and dial-down resources as needed

Public cloud

In the public cloud, all resources are owned and managed by the public cloud provider. The most popular public clouds are Amazon Web Services (AWS), Microsoft Windows Azure and Google Cloud Platform. Unlike the dedicated resources of the private cloud, all resources in the public cloud are shared (or pooled) among all public cloud customers. Because resources are shared across a large number of companies, the public cloud can often offer the lowest usage price.

Public cloud use cases:

In the preceding examples, the benefits of the public cloud include:

  • Reduced IT staff
  • Elimination of up-front capital equipment costs
  • Payment by resource usage or end-user seat licenses
  • Ability to dial-up or dial-down resources as needed, or easily add or reduce users
  • Reduced cost for organisations for storing archive-grade data that is rarely accessed
  • Reduced costs from economies of scale by sharing the expense of the physical servers, storage, and networking in a virtualised environment

Although the public cloud is a good fit for the use cases above, the performance, reliability, security, and data integrity levels in the public cloud may not meet business requirements when compared with the private cloud. In addition, for applications such as backing up data into the cloud, where large amounts of data must be moved into and out of the systems daily, the time to back up data into the cloud and recover all data from the cloud in the event of a primary site disaster could take weeks to months. This is due to limited available bandwidth on the sending side, provisioned bandwidth on the receiving side, and Internet/WAN latency.

Hybrid cloud

The hybrid cloud is a combination of onsite private cloud and offsite shared resources. Offsite shared resources can be provided by a wide range of service providers, from third-party hosting facilities to mass market public cloud providers. The choice of service provider is driven by your business requirements for availability, security, reliability, performance, auditability and recovery.

The benefits of the hybrid cloud are:

  • Dedicated resources onsite
  • Lower costs, due to using offsite shared resources versus offsite dedicated resources


'The cloud' represents a pool of computing resources delivered on an as-needed basis from a cloud provider's network, often eliminating the need for onsite equipment, maintenance, and management. IT departments can increase or decrease capabilities as needed without purchasing their own capital equipment and software, without training additional IT personnel, and without consuming additional rack space, power, and cooling. The following table summarises the strengths and weaknesses of the various cloud options:

Bill Andrews is the president and CEO of ExaGrid Systems