Cloud and Virtual Storage | OCR H446

Learning Objectives

By the end of this topic you will be able to:

Describe what cloud storage is and how it is implemented

Distinguish between cloud storage and virtual storage

Evaluate advantages and disadvantages of cloud storage

Explain thin provisioning and deduplication in virtual storage

Cloud Storage

What is Cloud Storage?

Cloud storage stores data on remote servers owned by a third-party provider (e.g. Google Drive, iCloud, AWS S3). Data is accessed over the internet rather than from local storage.

Scalable: capacity can be increased on demand without physical hardware changes at the user’s location.

Accessible anywhere: data available from any device with internet access.

Subscription model: pay for what you use. No upfront hardware costs. Provider manages maintenance and redundancy.

Cloud providers typically store multiple copies across different data centres (geographical redundancy) to protect against hardware failure or disaster.

Cloud Storage

Advantages and Disadvantages

Advantages

Scalable on demand

Accessible from any location/device

Automatic backups and redundancy

No local hardware maintenance

Easy file sharing and collaboration

Disadvantages

Requires reliable internet connection

Data security/privacy concerns (third-party control)

Ongoing subscription costs can exceed local storage long-term

Latency vs local storage

Data sovereignty issues (data stored abroad)

Virtual Storage

Virtual storage presents a logical view of storage that is larger than the physical storage available. The system manages the illusion of a larger storage space using techniques like thin provisioning.

Thin provisioning: storage space is allocated on-demand as it is actually used, rather than pre-allocating all space upfront. A volume may show 10 TB but only use 2 TB physically.

Deduplication: only one copy of duplicate data is stored. Multiple references point to the same physical block, saving space.

Compression: data stored in compressed form; decompressed on access. Reduces physical storage needs further.

Storage Area Networks

SAN and NAS

SAN (Storage Area Network)

A dedicated high-speed network connecting servers to shared storage arrays. Presents storage as block devices directly to servers. Used in enterprise environments requiring high performance.

NAS (Network Attached Storage)

A file-level storage server connected to a LAN. Multiple users access shared files over the network. Simpler to set up than SAN; used in homes, SMEs and media servers.

Both SAN and NAS can be virtualised — physical storage pooled and presented as logical volumes to clients. This forms the basis of modern cloud storage infrastructure.

Exam Practice

OCR H446 Style · 4 marks

Explain two disadvantages of using cloud storage compared to local storage for a business.

[4 marks]

Disadvantage 1 — Security/privacy: data is stored on third-party servers. The business loses direct control over its data [1]. A breach at the cloud provider could expose sensitive business data, and data may be subject to foreign law [1].

Disadvantage 2 — Internet dependency: cloud storage requires a reliable internet connection to access data [1]. If connectivity fails or the provider has downtime, the business cannot access its data, disrupting operations [1].

Common Mistakes

Don’t Lose Marks

Saying cloud storage is “free” — basic tiers may be free but commercial/business use involves subscription fees. Always mention cost as a factor in evaluation.

Confusing cloud storage with cloud computing — cloud storage refers specifically to remote file/data storage. Cloud computing covers a wider range of services (IaaS, PaaS, SaaS) including processing power.

Saying virtual storage means “storage in the cloud” — virtual storage is a logical abstraction of physical storage that can exist locally or remotely. Thin provisioning is the key technique.

Cloud and VirtualStorage