Hard disk drives and solid state drives are storage devices that use magnetic charges and flash memory respectively to store data. Hard drives have moving parts that allow vast storage but can wear out, while solid state drives have no moving parts and are faster but more expensive per gigabyte. Optical discs like CDs, DVDs, and Blu-Rays use microscopic bumps on reflective surfaces read by lasers to store data in various capacities depending on the technology. USB flash drives are solid state storage that can be easily connected via USB to transfer files.
Hard disk drives and solid state drives are storage devices that use magnetic charges and flash memory respectively to store data. Hard drives have moving parts that allow vast storage but can wear out, while solid state drives have no moving parts and are faster but more expensive per gigabyte. Optical discs like CDs, DVDs, and Blu-Rays use microscopic bumps on reflective surfaces read by lasers to store data in various capacities depending on the technology. USB flash drives are solid state storage that can be easily connected via USB to transfer files.
Hard disk drives and solid state drives are storage devices that use magnetic charges and flash memory respectively to store data. Hard drives have moving parts that allow vast storage but can wear out, while solid state drives have no moving parts and are faster but more expensive per gigabyte. Optical discs like CDs, DVDs, and Blu-Rays use microscopic bumps on reflective surfaces read by lasers to store data in various capacities depending on the technology. USB flash drives are solid state storage that can be easily connected via USB to transfer files.
Hard disk drives and solid state drives are storage devices that use magnetic charges and flash memory respectively to store data. Hard drives have moving parts that allow vast storage but can wear out, while solid state drives have no moving parts and are faster but more expensive per gigabyte. Optical discs like CDs, DVDs, and Blu-Rays use microscopic bumps on reflective surfaces read by lasers to store data in various capacities depending on the technology. USB flash drives are solid state storage that can be easily connected via USB to transfer files.
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What is a storage device?
• Storage devices are the computer hardware used to remember/store
data. What is a hard disk drive? • Hard disk drives are non-volatile magnetic storage devices capable of remembering vast amounts of data. • An electromagnet in the read/write head charges the disk’s surface with either a positive or negative charge, this is how binary 1 or 0 is represented. • The read/write head is then capable of detecting the magnetic charges left on the disk’s surface, this is how data is read. Organisation of data on a hard disk • The disk surface is divided into concentric circles (tracks) and sectors (wedges). Dividing the surface in this way provides physical addresses to remember where data is saved. • A circuit board carefully co-ordinates the rotating disk and swinging actuator arm to allow the read/write head to access any location very quickly. • Typical HDD capacities are measured in Terabytes (TB). • They can be installed inside a computer or purchased in a portable (external) format. Typical applications for hard disk drives • Desktop computers • Laptop computers • TV and satellite recorders • Servers and mainframes • Portable (external) drives are sometimes used to backup home computers or transfer large files Benefits Drawbacks • Capable of holding vast amounts • Due to the nature of its moving parts, they of data at affordable prices will eventually wear and break • Fast read and write speeds • Although very fast, waiting for the moving parts means it will never perform as fast • Reliable technology as solid state drives • Relatively small in size • More fragile and less robust than a solid state drive • Higher power consumption than a SSD • Some noise is created by the moving parts What is a solid state drive • Solid state drives are non-volatile storage devices capable of holding large amounts of data. • They use NAND flash memories (millions of transistors wired in a series on a circuit board), giving them the advantage of having no mechanical moving parts and therefore immediate access to the data. • Solid state drives perform faster then traditional hard disk drives, however they are significantly more expensive. • This expense means that typical capacities are usually measured in Gigabytes (GB). • They can be installed inside a computer or purchased in a portable (external) format. • Until we reach a point were large capacity SSDs are affordable, a compromise is to run two disk drives inside a computer. An SSD as the primary drive for your important programs and operating system, and a traditional HDD to store music, documents and pictures (which don’t need the faster access times). • The lack of moving parts in an SSD makes it very robust and reliable, ideal for a portable device. Typical applications for solid state drives • Smartphones • Tablet computers • High-end laptops • Two drive desktop solutions • Portable drives are sometimes used in HD video cameras Benefits Drawbacks
• Extremely fast read/write speeds • Expensive to buy (per GB)
• Small in physical size and very light, • Limited in capacity due to the ideal for portable devices expense • No moving parts to wear, fail or get damaged – ideal for making portable • Limited amount of writes computers and devices more reliable and durable • Uses less power than a HDD, increasing battery life time • Very quiet • Generates less heat What are optical storage discs? • CD, DVD and Blu-Ray drives are optical storage devices. • Binary data is stored as changes to the texture of the disc’s surface, sometimes thought of as microscopic pits and bumps. • These ‘bumps’ are located on a continuous spiral track, starting at the centre of the disc. • Whilst the disc is rotating at a constant speed, a laser is pointed at the spiral track of ‘bumps’. • The laser will reflect/bounce off the disc surface in different directions depending upon whether a 1 or 0 has been read. Disc capacities Typical applications for optical media • CD – Audio and small amounts of data • DVD – Standard definition movies and data • Blu-Ray – HD video and large amounts of data DVD • Despite being the same physical size, a DVD can hold more data than a CD. • To achieve this, a more tightly packed spiral track is used to store the data on the disc. • To accurately access the smaller ‘bumps’, a finer red laser is used in a DVD drive than that found in a standard CD drive. • To increase capacity further, DVDs are also capable of dual layering. This is a diagram showing the method used for CDs and DVDs to store and edit data, by things called “pits” and ‘bumps” on the reflective side of the disc. The length between the pits and the bumps are called the Wave length, the shorter the wave length, the more storage capacity there is. How CDs work? What is DVD-RAM? • DVD-RAM is an optical media storage device. • It differs from a traditional DVD in that data is stored in concentric tracks (like a HDD) which allows read and write operations to be carried out at the same time. • This means, for example, that when used in a personal video recorder you can record one television programme whilst watching a recording of another. This allows handy features such as ‘time slip’ to be possible. • When used within a CCTV system you could review footage whilst still recording your cameras. • The capacity of DVD-RAM is 4.7 GB, or 9.4 GB for double-sided discs. Typical applications for DVD-RAM • Personal and digital video recorders • High-end CCTV Benefits Drawbacks • Read and write at the same time • Disc speeds higher than 5x are • Can be rewritten to many more times than a less common traditional DVD-RW • Has write-protect tabs to prevent accidental • Less compatibility than DVD-RW deletion when used in an optional cartridge • Data is retained for an estimated 30 years. This long life is great for archiving data • Reliable writing of discs because the verification done by the hardware, not by software Blu-Ray • Blu-Ray technology squashes even more data into the same size disc as a CD or DVD. • The spiral data tracks on a Blu-Ray disc are so small a special blue (violet) laser has to be used to read the ‘bumps’. • Like a DVD, Blu-Ray discs are capable of storing data on multiple layers. The differences between Blu-ray, CDs and DVDs: • CD and DVD use red laser to read and write data while blu-ray disks use blue laser. • Blu-ray wavelengths are the closest to each other which means that more data can be stored and to a higher quality whereas CDs have the furthest wavelength. • CD- uses single 1.2 mm polycarbonate layer to be constructed • DVD uses two 0.6 mm polycarbonate layers, this method is called dual layering which increases the storage capacity. • Blu-ray uses single 1.1 mm polycarbonate layer • Track pitch (distance between tracks) – CD = 1.6 micrometers, DVD = 0.74 micrometers, Blu- ray = 0.3 micrometers. Optical media also come in different types: • ROM media have data pre-written on them. The data cannot be overwritten. Music, films, software and games are often distributed this way. • R media are blank. An optical device writes data to them by shining a laser onto the disc. The laser burns pits to represent '0's. The media can only be written to once, but read many times. Copies of data are often made using these media. • RW works in a similar way to R, except that the disc can be written to more than once. What is USB Flash Memory? • Flash are non-volatile solid state storage devices which use NAND flash memories to store data (millions of transistors). • USB refers to the USB connection that allows users to plug the device into the USB port of a computer. • Other types of flash storage include the memory cards used in digital cameras. • Flash memory comes in a variety of capacities to suit most budgets and requirements. Typical applications for flash memory • USB memory sticks – saving and transferring documents etc • Memory cards in digital cameras Benefits Drawbacks • Portable, small and lightweight • Limited (but huge) number of • Durability, flash has no moving write cycles possible parts to damage • Really high capacities are • Range of capacities available uncommon • Fast speeds, with no moving • In relative terms, an expensive parts of boot up time storage option compared to a HDD