CS: Virtual, Offline, and Cloud memory

CD

• Offline storage

• Optical media which uses a spiral track

• Red lasers are used to read and write data

• Dual-layering increases storage capacity

DVD

• Offline storage

• Optical media which uses concentric tracks to store data

• This allows read/write operations to be carried out at the same time

USB stick

• Offline memory

• Non volatile

• Uses NAND flash memories (millions of transistors)

• No moving parts

• Small, may get easily lost. USB connection often easily broken by being bent if not stored carefully.

Blu-ray discs

• Offline storage

• Have built-in encryption to a good choice for game and film producers

• Shortest wavelength of laser, so they have higher data capacity as more pit and lands can be created

CD, DVD vs Blu-ray

• CDs have lowest capacity, 600MB

• DVDs have around 5-9 GB

• Blu-Ray have shortest wavelength, around 25GB.

Solid state offline memory

• USB memory sticks

• Flash drives

• SD cards

• SSD (portable hard drive)

Magnetic offline memory

HDD

Virtual memory

• When the CPU is overwhelmed, they can run out of space in the RAM

• The operating system sections off some secondary storage and uses it to temporarily store data that was sitting in the RAM but isn’t currently being used

Why might virtual memory make a computer slower?

When the data in virtual memory is needed again, it has to be moved back into RAM, which makes the computer run slower as it takes more time to fetch the data.

Cloud computing

Storing of data on servers located on and accessed via the internet.

Advantages of cloud storage

• Cost efficiency as traditional storage means you must purchase storage capacity in anticipation of your need for it but this may end up unused. Cloud storage enables you to pay only for the capacity you need when you need it, and you don’t have to maintain or manage infrastructure on premises.

• Improved agility as you can provision and deploy a server in minutes, whereas purchasing and deploying the same server on premises may take a much longer time

• Greater scalability as cloud computing enables you to scale up or downsize on demand in response to rises and falls in data or traffic

• Reliability as most cloud providers have redundancy (the replicate data across more than one data centre) so it is easier to implement backup and recovery of data

• Security and performance as since technology is improving continuously, security offered by cloud service providers is steadily outstripping on-premises solutions.

Drawbacks of cloud computing

• Requires internet connectivity so if this goes down, users will be unable to access their data. Mobile data may be used to get around this.

• Moving cloud providers as moving an organisation’s computing to the cloud takes a lot of effort in terms of skills required, time, testing and user education. It may be too much work to move cloud providers once everything’s set up.

• Security risks as data breaches and hackers are always a threat.

• Lack of control as the resources are owned and operated by other companies so there may not be as much control as there would be with an organisation’s own on-premises infrastructure.

Public cloud

• Publicly shared resources

• Affordable access

• Consumer ‘rents’ a portion of the server storage from another company via the internet for a subscription or usage-based fee

• Supports multiple customers

• Suitable for less confidential information

Private cloud

• Cloud infrastructure operated exclusively for one organisation

• Managed by company or a third party or both

• Primarily on premises but can be hosted on a dedicated cloud provider

• Takes advantage of cloud efficiencies while having greater control over resources and security so suitable for secured confidential information

• Connectivity over internet, fibre and private network

Hybrid cloud

Integrates public and private clouds, allowing workloads to move seamlessly between both as needed

Multi-cloud

Infrastructure comprising multiple vendors’ public clouds