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What is public cloud storage?

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Public cloud storage is an easy way for businesses and end users to license storage capacity from a third party to store their digital data. This article categorizes public cloud storage into two classes: file storage for sharing and collaboration, and storage for business applications. 

Public cloud file services from companies like Dropbox, Box, Google, Microsoft SharePoint, and Apple iCloud offer easy-to-use repositories of file data for sharing, collaboration, and archiving. The target users include individuals and organizations of all sizes. 

Companies such as Microsoft, Amazon, Google, IBM, and others offer storage as a service (StaaS) to enable businesses to easily license, provision, and access storage capacity optimized for business application use, and to support software development, data analytics, databases, and other enterprise workloads. This article focuses  on this class of public cloud storage. Common characteristics of public cloud storage include:

  • Easy to deploy, self-provisioned capacity
  • Highly automated management with rich APIs
  • Dynamic capacity and performance scaling
  • Flexible storage offerings including file, object, and block storage access

Pay-as-you-go or subscription pricing

Benefits of using public cloud storage

Public cloud storage offers IT users a number of benefits.

  • Public cloud storage is easy to deploy through a web portal managed by the cloud provider or through a marketplace offering, such as the AWS Marketplace. No significant technical knowledge is required to deploy a storage container, because the cloud provider handles the management and maintenance of the environment.
  • Storage capacity can be dynamically scaled up or down as needs change. And the limits on capacity are high enough for most workloads.
  • Cloud storage is accessible from almost any location, because the interface to the storage environment is through a web browser over the internet. Cloud providers typically offer their services in a variety of geographic locations around the globe, allowing users to select a region closest to their business or to address any geographic or regulatory requirements. Additionally, most cloud providers offer multiple storage offerings, such as file services, object storage, and block storage, to meet the needs of most applications.
  • Agility, the ability to deploy the service quickly, is a primary benefit of any cloud service. This is true for storage as well. Licensing and deployment can often be done in less than an hour, which is much faster than procuring hardware, or in many cases even faster than submitting a ticket for capacity from corporate IT.
  • Most cloud providers offer flexible performance levels, allowing end users to deploy the right storage for the application. Performance tiers allow users to select and pay for the performance required, and even to change the tier dynamically to accommodate temporary increases or decreases in performance needs. Additionally, as organizations leverage more services in the cloud, having proximity of their data to the compute services offers performance advantages over maintaining data on the premises.
  • Although long-term economic advantages of cloud storage might be debated, few will argue about the economic benefits of procuring cloud storage for temporary uses like bursty workloads, for cyclical or seasonal projects, or even simply for backup and archive. The amount of capital and management overhead associated with on-premises storage for these uses might be higher than the cost of the storage capacity. As applications in the cloud become a higher priority, storing and maintaining data close to the applications becomes even more advantageous.

Disadvantages of using public cloud storage

As with most things in life, a strength can also be a weakness.

  • Storing data in the cloud can result in higher than expected storage costs. This is especially true if the data is being accessed frequently outside of the cloud, because egress charges for pulling data out of the cloud are relatively high. Additionally, depending on the tier or type of storage, long-term storage usage in the cloud can add up quickly.
  • Performance o public cloud storage is generally good for most applications. However, because the storage is located in a shared environment, performance is typically not as good as what is achievable on the premises. This is true for throughput, IOPs, and latency.
  • Public cloud storage is deployed as a virtual storage container managed by a cloud provider in their own data center(s). As a result, the end user has little knowledge or control where the data resides outside of the selected geographic region or storage class/tier. This limited control may be challenging for organizations that manage regulated data or valuable data such as intellectual property.
Availability. Cloud public storage is commonly advertised to support three 9’s of availability, or 99.9% uptime.  This means, on average, not quite 9 hours of downtime per year, or about 10 minutes per week. In order to achieve higher levels of uptime, some users mirror storage between two instances of cloud storage. This approach results in higher overall cost.

Differences between public and private cloud storage

Private cloud storage is an approach that offers a public cloud storage experience on the premises. The goal of private cloud storage is to deliver the advantages of public cloud while minimizing the related disadvantages. The technologies used, such as scalable storage, virtual or software-defined technologies, deployment automation, and rich APIs, allow organizations to configure their storage environment to best meet their application and user needs. 


  • The overall cost of storage can be reduced by procuring and managing a private cloud. Deploying a private cloud storage infrastructure requires either capital expenses or financing to stretch the purchase over a predetermined period of time. Often, however, the amount of use achieved from the storage infrastructure means that over the life of the purchase, the cost per capacity is typically less than if deployed in a public cloud.
  • The private cloud storage infrastructure is a shared infrastructure within the organization, but the environment can be more effectively sized and tuned to the needs of the business. Additionally, latency and other performance degradations associated with large publicly shared data centers are minimized.
  • Higher levels of control and security can be achieved with private cloud storage when compared to public cloud storage. Private clouds are deployed in the data center or in a controlled environment, such as a colocation facility, that is managed by IT personnel within the organization.


Cost. Although the cost of capacity is typically much lower with a private cloud environment, organizations that deploy a private cloud must account for the additional IT resources, facilities, and environment costs associated with procuring, managing, and deploying IT equipment.

Cost of running a public cloud storage

Pricing public cloud storage isn’t a one-sentence answer, because multiple flavors of storage offerings are available. However, it’s important to understand where you will generally incur cost.

  1. Storage type. Each public cloud provider offers multiple storage services, such as object storage, file storage, and block storage. Each of these storage types has its own capacity and performance limits, and many offer various cost and performance tiers within each storage type. Typically, the most cost-effective and lowest-performing storage is object storage, and the most costly and highest performing is block storage.
  2. Disk capacity. Each of the storage types is commonly licensed on a capacity basis, and in many cases performance is tied to capacity up to a maximum limit. If you need higher performance, you will get it with higher capacity.
  3. As mentioned previously, performance scaling for most storage services is closely tied to capacity. Therefore, the greater the performance required, the more capacity is delivered. Some storage services also offer tiered performance levels that allow cost and performance to be better aligned and less dependent on capacity.
  4. Egress charges. One cost that is often not planned for is egress charges, the costs charged by the amount of data that exits the service provider’s gateway. For users who transfer data in and out of the cloud, this cost can over time be as much as or more than the underlying storage cost. Therefore, application and workload I/O characteristics should be considered when evaluating public cloud storage.
Advanced data management. For those looking for more advanced features than what cloud providers offer, third-party vendors offer data management software that uses  the disk capacity of native public cloud storage, and then layer advanced data management such as deduplication, compression, snapshots, clones, and other capabilities to enhance the value of the cloud storage. This advanced data management is an incremental charge over the disk capacity of the native storage, but in some cases, enabling the data reduction features can result in a combined cost that is much lower than simply the native storage costs.
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