INFO1 – Practical problem solving in the digital world 3.1 Storage Devices INFO1 – Practical problem solving in the digital world

Reasons for storing data Basic setup information and operating systems are required for the computer to function. Application software needs to be available for the user to carry out tasks. Files created by the user need to be stored so that they can be used again. Data may need to be transferred from one device to another. Backup copies needs to be taken in case the original files are lost or corrupted.

Magnetic Storage Optical Storage Storing data on a computer Online Storage Flash Memory

Internal & External Storage When a PC boots up it uses data stored in the ROM to load the BIOS to make the computer work. It loads the operating system from the hard drive. Application software and data files are called up from the hard drive as the user requests them. Hard drive and ROM are internal storage devices.

Internal & External Storage In addition to immediate storage of ROM and RAM, a computer needs a backing store for mass storage of data and programs. Most PC’s also make use of removable media. External hard drives connected by USB are used. DAT tapes are used in back up severs. Portable flash drives are used for various file storage.

Storage Media Vs Storage Device What’s the difference? The storage medium is the surface on which the data is stored. The storage device is the hardware that reads the data. E.g. a DVD re-writer is the device that reads and writes data to DVD media.

These devices work by storing data on magnetised surfaces. Magnetic Storage… These devices work by storing data on magnetised surfaces.

Hard Disks Most of the storage on a PC system is carried out by the hard disk. They are made from rotating plastic/metal disks covered by a magnetic coating where data is stored. Read/Write heads move between the disks as they spin to read/write the data. Available with very large storage capacities. Very fast, reliable and robust. External hard disks are portable.

RAID / Mirrored Drives RAID drives are a set of disks that work together. Each disk can be used to store a part of the data. If one drive fails then the others take over to ensure data is not lost, this can prevent network failure. Mirrored drives can be set up so more than one copy of the data exists, in case of drive failure. In servers these can be hot swapped.

Floppy Discs Were once a very popular method of storage, but only hold 1.44mb of data. Now obsolete as they are impractical for today's vast amounts of data. Most pc’s do not even come with a floppy drive any more. They store data on a circular pieces of magnetic film. Very easily damaged, not very reliable.

DAT tapes Small tapes that can hold a lot of data. Often used in backup servers as they are Easy to take away and store in a different place to the server. Slow to write to and slow to retrieve data from. Less reliable than hard drives. But useful as a backup medium.

Optical Storage Use devices such as CD’s and DVD’s and use optical technology to etch data onto a plastic coated metal disc. Laser beams are then passed over the surface to read the data. CD’s have up to 700Mb capacity DVD’s have 4.7Gb capacity Blue ray offers even more capacity.

CD-ROM, CD-R, CD-RW CD-ROM/ DVD-ROM CD-R/ DVD-R CD-RW/ DVD-RW ROM – Read Only Memory. Often used to supply software. No further data can be written to them. Have data written to them once. No more data can be written to them. Good for backup storage of data. RW – Re-write. Data can be written to them many times. Good for transferring data between computers. They are all good portable devices, but have limited storage capacity and can be scratched easily making data unreadable.

Flash Memory Small in size so are used for cameras, MP3 players, mobile phones, sat-nav’s etc. It uses solid state technology to store data on tiny cards of various sizes. Flash based pen drives (USB) are very popular for transferring data between computers. Most operating systems recognise them, so there is no need for installation. Solid state memory is now being used for laptops and other portable computers.

Online Storage Increased upload and download speeds have enabled broadband internet connections. This has made it feasible for people to store their data away from their computers. Many websites offer a storage service with a high capacity for a small price or even for free. This is convenient as you do not need to carry a portable device. However an internet connection must be available.

Examiners tips… If a question asks you to choose a medium to save data to, make sure you choose CD-R or CD-RW rather than a CD-ROM, because CD-ROMs are read only. The same applies to DVD. Never choose floppy disc as an answer to a question asking you to recommend a backup medium. They hold too little data and there are much more reliable methods available.

Storage sizes Terabyte (TB) 1,000 gigabytes (1,024 Gb)