私有云与公共云

Cloud deployment models can vary with the needs of organizations. Two fundamental cloud deployment models, private cloud and public cloud differ based on who owns and controls the cloud. Private clouds are owned and used by a single tenant, separated from the public internet and other systems using firewalls. A public cloud is open to the public Internet, where cloud service providers (CSP) can serve multiple tenants many different services.

A public cloud, in contrast to a private cloud, is a pool of shared computing resources owned by a cloud service provider (CSP) and delivered to cloud consumers via the public Internet. Cloud consumers can select from numerous cloud configurations tailored to their needs and sign up for pay-as-you-go payment programs. These options give consumers tremendous technological flexibility and control over IT expenses. Because the CSP model assumes responsibility for maintaining hardware, application, and bandwidth, organizations can easily set up deployments and later extend them when demand increases without the burden of managing the underlying infrastructure.

For many types of organizations, the shared cloud resources model is an enabling technology. A small software development firm never needs to own servers, they can simply utilize a platform-as-a-service provider and begin development with little upfront IT costs. For larger content delivery enterprises, utilizing public cloud data centers is a redundancy strategy that can ensure content remains reliably accessible during peak times. CSPs match those needs, growing and shrinking resources to prevent under and overprovisioned, needlessly inflating costs.

For organizations that deploy private clouds, their primary advantage is also their primary disadvantage. Private clouds grant the power of complete cloud control, but with power comes the responsibility of ownership, think maintenance, upgrades, troubleshooting, security, etc. The following are some prominent advantages and disadvantages to consider.

Private Cloud Advantages

• Complete Control Over Technology Choices — Complete control over every technology choice is a powerful aspect of private clouds. For enterprise clients that may have integrated hundreds of systems and thousands of services across regions, a private cloud may be the only option for keeping these systems aligned.
• Maximum Security and Privacy — Stemming from the advantage of fullcontrol comes maximum security and privacy. Private cloud owners build their clouds behind firewalls, controlling all traffic in and out, and if desired, they can be cut off from the public Internet altogether.
• Near-Zero Latency — Public cloud resources simply cannot beat the latency of local resources.

Private Cloud Disadvantages

• Full Responsibility — Private clouds are owned and operated by the consumer of the same cloud. That means all overhead and responsibilities for maintaining the private cloud must be assumed by the cloud owner. Unless the cloud owner hires a managed private cloud where a professional service is put in charge of maintaining all the aspects of the cloud.
• Cost Disadvantage — Private clouds are expensive because costs can go up and down depending on the behavior and usage of the private cloud. Whereas, agreeing to a service level agreement (SLA) with a cloud provider guarantees that prices remain consistent and predictable. For instance, an unanticipated cyberattack that cripples a private cloud can be expensive to defend and recover from, but that is a security cost that can be included in SLAs.
• Technology Obsolescence — Linked to costs in a way, when technology needs to be upgraded, private clouds rely on in-house IT staff expertise and pay in the time to upgrade. When technology becomes obsolete, the organization makes another capital expenditure for newer technology or risk falling behind. Upgrades and innovations are factored into most public cloud services. Cloud consumers don’t need to worry about falling behind, the best CSPs will seamlessly update and upgrade their infrastructures, unnoticed to the consumer.

Hybrid deployments have successfully merged both public and private cloud, in effect lessening the disadvantages while making the advantages from both deployment types available to IT teams.

Private cloud and public cloud benefits are not exclusive in today’s cloud landscape, primarily because public cloud providers have worked diligently to offer services that rival private clouds. However, many of the benefits of the private cloud are wholly unique, such as complete control over all aspects of hardware, software, and connectivity, which appeals to organizations in need of maximum security and customization.

Private Cloud Benefits

• Complete Control — Private clouds are owned and operated by the cloud consumer, giving them full domain control over all aspects of their cloud infrastructure, configuration, and access.
• Maximum Customizability — Private cloud owners have maximum control over protocols, compliance, configurations, etc. For certain use cases, such as optimization of applications that do not easily translate to public cloud systems.
• Security Control, Privacy, and Autonomy — No matter how secure public cloud resources can be, traffic that poses security risks will still traverse the public Internet. Private cloud dramatically improves data privacy and security.

Public Cloud Benefits

• Reduced Risks — Performance, maintenance, upgrades, downtime, and reliability are all things that IT staff would no longer need to worry about on the day-to-day.
• Virtually Infinite Elasticity and Scalability — Public cloud models promise a perceived infinite elasticity and scalability (since hardware disappears to consumers), so when tenant system workloads ramp up they can reliably be served to users.
• Innovation — Economies of scale allow public cloud providers to offer the latest innovative technologies to their customers. Perhaps even upgrading performance features that improve even basic cloud use, such as better storage management, or security software all without concerning tenant IT staff.