At the core of all cloud services, products, and solutions are software tools with three underlying pillars of functionality:

1. Processing data and running applications (compute servers)
2. Moving data (networking)
3. Preserving or storing data (storage)

Cloud Storage Services

Cloud storage is basically defined as data storage that is made available as a service via a network. Products and solutions are the most common cloud storage service building blocks of physical storage systems. Private cloud and public services from software as a service (SaaS) to platform as a service (PaaS) and infrastructure as a service (IaaS) leverage tiered storage, including solid-state drives (SSDs) and hard disk drives (HDDs).

Similar to traditional enterprise storage environments, cloud services and solution providers exploit a mix of different storage technology tiers that meet different service-level objectives (SLOs) and service-level agreement (SLA) requirements. For example, using fast SSDs for dense I/O consolidation—supporting database journals and indices, metadata for fast lookup, and other transactional data—enables more work to be performed with less energy in a denser and more cost-effective footprint.

Using a mixture of ultrafast SSDs along with high-capacity HDDs provides a balance of performance and capacity to meet other service requirements with different service cost options. With cloud services, instead of specifying what type of physical drive to buy, cloud service providers cater to differing customer needs by providing various availability, cost, capacity, functionality, and performance options to meet different SLA and SLO requirements.

IaaS Storage Types

IaaS uses the following storage types:

• Ephemeral storage: This type of storage is relevant for IaaS instances and exists only as long as its instance is up. It will typically be used for swap files and other temporary storage needs and will be terminated with its instance. This storage type is non-persistent and normally exists within the compute infrastructure with virtual instances, not as part of the persistent storage infrastructure.
• Raw storage: Raw device mapping (RDM) is an option in some server virtualization environments that enable a storage logical unit number (LUN) to be directly connected to a virtual machine (VM) from the storage area network (SAN), which will typically exist within the volume storage infrastructure
• Long-term storage: Some vendors offer a cloud storage service tailored to the needs of data archiving. This includes features such as search, guaranteed immutability, and data lifecycle management. Some archiving services can use an on-premises appliance that connects to customers’ data stores via APIs and allows search. Long term storage can use either Volume or Object storage infrastructure.
• Volume storage: A virtual hard drive that can be attached to a virtual machine instance and be used to host data within a file system. Volumes attached to IaaS instances behave just like a physical drive or an array does. Examples include Amazon EBS and Oracle Block Volume.
• Object storage: Object storage is like a file share accessed via APIs or a web interface. Examples include Amazon S3 and Oracle Object Storage.

Any of these IaaS storage types can usually be accessed using an API call from a PaaS service or presented to an end user as SaaS using a customized interface.

PaaS Storage Types

Cloud platform services, or platform as a service (PaaS), are used for applications and other development, while providing cloud components to software. What developers gain with PaaS is a framework they can build upon to develop or customize applications. PaaS makes the development, testing, and deployment of applications quick, simple, and cost effective. With this technology, enterprise operations or a third-party provider can manage OSs, virtualization, servers, storage, networking, and the PaaS software itself. Developers, however, manage the applications.

PaaS utilizes the following data storage types:

• Databases: Usually multitenant databases as a service. Can be accessed via APIs or direct calls. Each customer’s data is segregated and isolated from other tenants. The database usually utilizes volume storage shared by multiple database instances.
• Big data as a service: Big data is data whose velocity, variety, and volume require the use of new technical architectures and analytics. Geolocation and other big data applications may be offered as a cloud platform. Data is typically stored in object storage or in another distributed file system. Data typically needs to be close to the processing environment and may be moved as needed for processing.

SaaS Storage Types

Cloud application services, or software as a service (SaaS), use the web to deliver applications that are managed by third-party vendors and whose interfaces are accessed on the client’s side.

Many SaaS applications can be run directly from a web browser without any downloads or installations required, although some require small plugins. With SaaS, it is easy for enterprises to streamline their maintenance and support because vendors can manage everything: applications, runtime, data, middleware, OSs, virtualization, servers, storage, and networking. Popular SaaS offering types include email and collaboration, customer relationship management, and healthcare–related applications.

SaaS utilizes the following data storage types:

• Information storage and management: Data is entered into the system via the web interface and stored within the SaaS application (usually a back-end database). This data storage utilizes databases, which in turn are installed on object or volume storage.
• Content/file storage: File-based content is stored within the application.
• Content delivery network (CDN): Content is stored in object storage, which is then distributed to multiple geographically distributed nodes to improve internet consumption speed.

Related article – Cloud Data Storage: Key Threats