Types
On prem
IaaS - Infrastructure as a Service
examples: DigitalOcean, Linode, Rackspace, Amazon Web Services (AWS), Cisco Metapod, Microsoft Azure, Google Compute Engine (GCE)
made of highly scalable and automated compute resources
is fully self-service for accessing and monitoring computers, networking, storage, and other services
allows businesses to purchase resources on-demand and as-needed instead of having to buy hardware outright
Delivery
delivers cloud computing infrastructure, including servers, network, operating systems, and storage, through virtualization technology
are typically provided to the organization through a dashboard or an API, giving IaaS clients complete control over the entire infrastructure. IaaS provides the same technologies and capabilities as a traditional data center without having to physically maintain or manage all of it
clients can still access their servers and storage directly, but it is all outsourced through a “virtual data center” in the cloud
clients are responsible for managing aspects such as applications, runtime, OSes, middleware, and data.
providers of the IaaS manage the servers, hard drives, networking, virtualization, and storage. Some providers even offer more services beyond the virtualization layer, such as databases or message queuing
Advantages
The most flexible cloud computing model
Easy to automate deployment of storage, networking, servers, and processing power
Hardware purchases can be based on consumption
Clients retain complete control of their infrastructure
Resources can be purchased as-needed
Highly scalable
Characteristics
Resources are available as a service
Cost varies depending on consumption
Services are highly scalable
Multiple users on a single piece of hardware
Organization retain complete control of the infrastructure
Dynamic and flexible
When to Use
Startups and small companies may prefer IaaS to avoid spending time and money on purchasing and creating hardware and software.
Larger companies may prefer to retain complete control over their applications and infrastructure, but they want to purchase only what they actually consume or need.
Companies experiencing rapid growth like the scalability of IaaS, and they can change out specific hardware and software easily as their needs evolve.
IaaS offers plenty of flexibility and scalability.
Limitations & Concerns
Security
While the customer is in control of the apps, data, middleware, and the OS platform, security threats can still be sourced from the host or other virtual machines (VMs).
Insider threat or system vulnerabilities may expose data communication between the host infrastructure and VMs to unauthorized entities.
Legacy systems operating in the cloud
While customers can run legacy apps in the cloud, the infrastructure may not be designed to deliver specific controls to secure the legacy apps.
Minor enhancement to legacy apps may be required before migrating them to the cloud, possibly leading to new security issues unless adequately tested for security and performance in the IaaS systems
Internal resources and training
Additional resources and training may be required for the workforce to learn how to effectively manage the infrastructure.
Customers will be responsible for data security, backup, and business continuity.
Due to inadequate control into the infrastructure however, monitoring and management of the resources may be difficult without adequate training and resources available inhouse
Multi-tenant security
Since the hardware resources are dynamically allocated across users as made available, the vendor is required to ensure that other customers cannot access data deposited to storage assets by previous customers
Similarly, customers must rely on the vendor to ensure that VMs are adequately isolated within the multitenant cloud architecture.
PaaS - Platform as a Service
examples: AWS Elastic Beanstalk, Windows Azure, Heroku, Force.com, Google App Engine, Apache Stratos, OpenShift
Cloud platform services
provide cloud components to certain software while being used mainly for applications
delivers a framework for developers that they can build upon and use to create customized applications
All servers, storage, and networking can be managed by the enterprise or a third-party provider while the developers can maintain management of the applications
Delivery
is similar to SaaS, except instead of delivering the software over the internet, PaaS provides a platform for software creation
delivered via the web, giving developers the freedom to concentrate on building the software without having to worry about operating systems, software updates, storage, or infrastructure.
allows businesses to design and create applications that are built into the PaaS with special software components
These applications, sometimes called middleware, are scalable and highly available as they take on certain cloud characteristics.
Advantages
Simple, cost-effective development and deployment of apps
Scalable
Highly available
Developers can customize apps without the headache of maintaining the software
Significant reduction in the amount of coding needed
Automation of business policy
Easy migration to the hybrid model
Characteristics
Builds on virtualization technology, so resources can easily be scaled up or down as your business changes
Provides a variety of services to assist with the development, testing, and deployment of apps
Accessible to numerous users via the same development application
Integrates web services and databases
When to Use
can streamline workflows when multiple developers are working on the same development project
If other vendors must be included, PaaS can provide great speed and flexibility to the entire process
if you need to create customized applications
can greatly reduce costs and it can simplify some challenges that come up if you are rapidly developing or deploying an app.
Limitations & Concerns
Data security
Organizations can run their own apps and services using PaaS solutions, but the data residing in third-party, vendor-controlled cloud servers poses security risks and concerns
Your security options may be limited as customers may not be able to deploy services with specific hosting policies
Integrations
he complexity of connecting the data stored within an onsite data center or off-premise cloud is increased, which may affect which apps and services can be adopted with the PaaS offering.
Particularly when not every component of a legacy IT system is built for the cloud, integration with existing services and infrastructure may be a challenge.
Vendor lock-in
Business and technical requirements that drive decisions for a specific PaaS solution may not apply in the future.
If the vendor has not provisioned convenient migration policies, switching to alternative PaaS options may not be possible without affecting the business
Customization of legacy systems
PaaS may not be a plug-and-play solution for existing legacy apps and services.
Instead, several customizations and configuration changes may be necessary for legacy systems to work with the PaaS service.
The resulting customization can result in a complex IT system that may limit the value of the PaaS investment altogether
Runtime issues
In addition to limitations associated with specific apps and services, PaaS solutions may not be optimized for the language and frameworks of your choice
Specific framework versions may not be available or perform optimally with the PaaS service
Customers may not be able to develop custom dependencies with the platform
Operational limitation
Customized cloud operations with management automation workflows may not apply to PaaS solutions, as the platform tends to limit operational capabilities for end users.
Although this is intended to reduce the operational burden on end users, the loss of operational control may affect how PaaS solutions are managed, provisioned, and operated
SaaS - Software as a Service
examples: Google Workspace, Dropbox, Salesforce, Cisco WebEx, Concur, GoToMeeting
cloud application services
utilizes the internet to deliver applications, which are managed by a third-party vendor, to its users.
A majority of SaaS applications run directly through your web browser, which means they do not require any downloads or installations on the client side.
Delivery
eliminates the need to have IT staff download and install applications on each individual computer
vendors manage all potential technical issues, such as data, middleware, servers, and storage, resulting in streamlined maintenance and support for the business.
Advantages
reducing the time and money spent on tedious tasks such as installing, managing, and upgrading software. Thus more time spent on delivering features
Characteristics
Managed from a central location
Hosted on a remote server
Accessible over the internet
Users not responsible for hardware or software updates
When to Use
Startups or small companies that need to launch ecommerce quickly and don’t have time for server issues or software
Short-term projects that require quick, easy, and affordable collaboration
Applications that aren’t needed too often, such as tax software
Applications that need both web and mobile access
Limitations & Concerns
Interoperability
Integration with existing apps and services can be a major concern if the SaaS app is not designed to follow open standards for integration
organizations may need to design their own integration systems or reduce dependencies with SaaS services, which may not always be possible/feasible
Vendor lock-in
Vendors may make it easy to join a service and difficult to get out of it.
the data may not be portable–technically or cost-effectively–across SaaS apps from other vendors without incurring significant cost or inhouse engineering rework
Not every vendor follows standard APIs, protocols, and tools, yet the features could be necessary for certain business tasks.
Lack of integration support
Many organizations require deep integrations with on-premise apps, data, and services
The SaaS vendor may offer limited support in this regard, forcing organizations to invest internal resources in designing and managing integrations
The complexity of integrations can further limit how the SaaS app or other dependent services can be used.
Data security
Large volumes of data may have to be exchanged to the backend data centers of SaaS apps in order to perform the necessary software functionality
ransferring sensitive business information to public-cloud based SaaS service may result in compromised security and compliance in addition to significant cost for migrating large data workloads
Customization
Since a one-size-fits-all solution does not exist, users may be limited to specific functionality, performance, and integrations as offered by the vendor
In contrast, on-premise solutions that come with several software development kits (SDKs) offer a high degree of customization options.
Lack of control
involves handing control over to the third-party service provider. These controls are not limited to the software–in terms of the version, updates, or appearance–but also the data and governance
Customers may therefore need to redefine their data security and governance models to fit the features and functionality of the SaaS service
Feature limitations
Since SaaS apps often come in a standardized form, the choice of features may be a compromising tradeoff against security, cost, performance, or other organizational policie
vendor lock-in, cost, or security concerns may mean it’s not viable to switch vendors or services to serve new feature requirements in the future.
Performance and downtime
Because the vendor controls and manages the SaaS service, your customers now depend on vendors to maintain the service’s security and performance.
Planned and unplanned maintenance, cyber-attacks, or network issues may impact the performance of the SaaS app despite adequate service level agreement (SLA) protections in place.
Differences
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