Cloud storage is a service model in which data is transmitted and stored on remote storage systems, where it is maintained, managed, backed up and made available to users over a network (typically the internet). Users generally pay for their cloud data storage on a per-consumption, monthly rate. Although the per-gigabyte cost has been radically driven down, cloud storage providers have added operating expenses that can make the technology considerably more expensive to use. The security of cloud storage services continues to be a concern among users. Service providers have tried to allay those fears by enhancing their security capabilities by incorporating data encryption, multi-factor authentication and improved physical security into their services.
Types of cloud storage
There are three main cloud-based storage access models: public, private and hybrid.
Public cloud storage services provide a Multi-tenant storage environment that is most suited for unstructured data on a subscription basis. Data is stored in the service providers’ data centers with storage data spread across multiple regions or continents. Customers generally pay on a per-use basis similar to the utility payment model; in many cases, there are also transaction charges based on the frequency and the volume of data being accessed. This market sector is dominated by Amazon Simple Storage Service (S3), Amazon Glacier for cold or deep archival storage, Google Cloud Storage, Google Cloud Storage Nearline for cold data and Microsoft Azure.
Private cloud storage service is provided by in-house storage resources deployed as a dedicated environment protected behind an organization’s firewall. Internally hosted private cloud storage implementations emulate some of the features of commercially available public cloud services, providing easy access and allocation of storage resources for business users, as well as object storage protocols. Private clouds are appropriate for users who need customization and more control over their data, or who have stringent data security or regulatory requirements.
Hybrid cloud is a mix of private cloud storage and third-party public cloud storage services with a layer of orchestration management to integrate operationally the two platforms. The model offers businesses flexibility and more data deployment options. An organization might, for example, store actively used and structured data in an on-premises cloud, and unstructured and archival data in a public cloud. A hybrid environment also makes it easier to handle seasonal or unanticipated spikes in data creation or access by “cloud bursting” to the external storage service and avoiding having to add in-house storage resources. In recent years, there has been increased adoption of the hybrid cloud model. Despite its benefits, a hybrid cloud presents technical, business and management challenges. For example, private workloads must access and interact with public cloud storage providers, so compatibility and reliable, ample network connectivity are very important factors. An enterprise-level cloud storage system should be scalable to suit current needs, accessible from anywhere and application-agnostic.
Cloud storage characteristics
Cloud storage is based on a virtualized infrastructure with accessible interfaces, near-instant elasticity and scalability, multi-tenancy and metered resources. Cloud-based data is stored in logical pools across disparate, commodity servers located on-premises or in a data center managed by a third-party cloud provider. Using the RESTful API, an object storage protocol stores a file and its associated metadata as a single object and assign it an ID number. When content needs to be retrieved, the user presents the ID to the system and the content is assembled with all its metadata, authentication and security.
In recent years, object storage vendors have added file system functions and capabilities to their object storage software and hardware largely because object storage was not being adopted fast enough. For example, a cloud storage gateway can provide a file system emulation front end to their object storage; that arrangement often allows applications to access the data without actually supporting an object storage protocol. All backup applications use the object storage protocol, which is one of the reasons why online backup to a cloud service was the initial successful application for cloud storage.
Most commercial cloud storage services use vast numbers of hard drive storage systems mounted in servers that are linked by mesh-like network architecture. Service providers have also added high-performance layers to their virtual storage offerings, typically comprising some type of solid-state drives (SSDs). High-performance cloud storage is generally most effective if the servers and applications accessing the storage are also resident in the cloud environment.
Companies that use public cloud storage need to have the appropriate network access to the hosting service.
Benefits of cloud storage
Cloud storage provides many benefits that result in cost-savings and greater convenience for its users. These benefits include:
Pay for what is used. With a cloud storage service, customers only pay for the storage they actually use so there’s no need for big capital expenses. While cloud storage costs are recurring rather than a one-time purchase, they are so low that even as an ongoing expense they may still be less than the cost of maintaining an in-house system.
Utility billing. Since customers only pay for the capacity they’re using, cloud storage costs can decrease as usage drops. This is in stark contrast to using an in-house storage system, which will likely be over configured to handle anticipated growth; so, a company will pay for more than it needs initially, and the cost of the storage will never decrease.
Global availability. Cloud storage is typically available from any system anywhere at any time; one does not have to worry about operating system capability or complex allocation processes.
Ease of use. Cloud storage is easier to access and use, so developers, software testers and business users can get up and running quickly without having to wait for IT to allocate and configure storage resources.
Offsite security. By its very nature, public cloud storage offers a way to move copies of data to a remote site for backup and security purposes. Again, this represents a significant cost-savings when compared to a company maintaining its own remote facility.
An in-house cloud storage system can offer some of the above ease-of-use features of a public cloud service, but it will lack much of the storage capacity flexibility of public service. Some hardware vendors are trying to address this issue by allowing their customers to turn on and off capacity that has already been installed in their arrays.
Drawbacks of cloud storage
There are some shortcomings to cloud storage — particularly the public services — that may deter companies from using these services or limit how they use them.
Security is the single most cited factor that may make a company reluctant — or at least cautious — about using public cloud storage. The concern is that once data leaves a company’s premises, the company no longer has control over how it’s handled and stored. There are also concerns about storing data that is regulated by specific compliance laws. Cloud providers address these concerns by making public the steps they take to protect their customers’ data, such as encryption for data in flight and at rest, physical security and storing data at multiple locations.
Access to data stored in the cloud may also be an issue and could significantly increase the cost of using cloud storage. A company may need to upgrade its connection to the cloud storage service to handle the volume of data it expects to transmit; the monthly cost of an optical link can run into the thousands of dollars.
A company may run into performance issues if its in-house applications need to access the data it has stored in the cloud. In those cases, it will likely require either moving the servers and applications into the same cloud or bringing the necessary data back in-house.
If a company requires a lot of cloud storage capacity and frequently moves its data back and forth, the monthly costs can be quite high. Compared to deploying the storage in-house, the ongoing costs could eventually surpass the cost of implementing and maintaining the on-premises system.