What do “on-prem” and “cloud” actually mean?

On-prem (on-premises) infrastructure refers to servers, storage, and networking equipment that are physically located at a business site and maintained by the organisation or its IT provider.

Cloud infrastructure refers to systems hosted in external data centres and accessed over the internet. This can include cloud-hosted servers, cloud platforms, and fully cloud-based applications.

In practice, many businesses operate a mix of both rather than choosing a single model.

Not all cloud is the same

When comparing on-prem and cloud, it’s important to understand that “the cloud” isn’t one thing.

Common cloud models include:

• Software as a Service (SaaS) Applications delivered entirely from the cloud (e.g. email, collaboration tools). Infrastructure is largely abstracted away, but configuration and data protection still matter.

• Infrastructure as a Service (IaaS) Virtual servers hosted in the cloud that resemble traditional servers.Provides flexibility but still requires active management.

• Hybrid environments A combination of on-prem and cloud systems working together.Often used during migration or where legacy systems remain on-site.

Each model shifts costs, control, and responsibility in different ways.

Cost comparison: how spending behaves over time

Cost is often the first comparison — but it’s also the most misunderstood.

On-prem costs typically include:

• Upfront hardware purchases

• Refresh cycles every few years

• Power, cooling, and physical space

• Maintenance and support

• Backup and disaster recovery infrastructure

Cloud costs typically include:

• Ongoing subscription or usage-based charges

• Storage and data transfer costs

• Security and backup services

• Management and optimisation

Cloud often reduces upfront capital spend, but costs can rise if usage isn’t monitored. On-prem costs are more predictable but less flexible.

The key difference is how costs scale and change over time, not just the headline numbers.

Reliability and downtime risk

Infrastructure choice has a direct impact on downtime exposure.

On-prem environments

• Dependent on local hardware

• Vulnerable to power, cooling, and physical failures

• Disaster recovery often complex and expensive

Cloud environments

• Built on redundant infrastructure

• Designed for high availability

• Less exposed to local physical issues

However, cloud availability still depends on:

• Internet connectivity

• Identity services

• Configuration choices

Cloud reduces many risks, but poor design can still cause outages.

Security and risk management

Security is often framed as “on-prem vs cloud”, but the reality is more nuanced.

On-prem security

• Full control over infrastructure

• Security depends heavily on patching, monitoring, and configuration

• Often limited by time, tools, and budget

Cloud security

• Strong platform-level protections

• Shared responsibility model

• Identity-centric security controls

In both models, most breaches occur due to:

• Weak credentials

• Poor access controls

• Lack of monitoring

The difference is how security is implemented and managed, not where systems are hosted.

Scalability, flexibility, and growth

Infrastructure decisions affect how easily a business can adapt.

On-prem

• Capacity is fixed unless hardware is upgraded

• Scaling often requires planning and downtime

• Expansion to new locations can be complex

Cloud

• Capacity can be increased or reduced quickly

• Supports temporary or seasonal demand

• Easier to support remote and multi-site teams

For growing businesses, flexibility is often a key driver toward cloud adoption.

Control, compliance, and data considerations

Some organisations assume on-prem equals control and cloud equals risk. In reality, control is more about governance and visibility.

Key considerations include:

• Data residency and regulatory requirements

• Access auditing and logging

• Retention and deletion policies

• Third-party access and integrations

Both on-prem and cloud environments can meet compliance requirements — but only when designed correctly.