Comparison of Secondary storage devices

Comparison of Secondary storage devices

Seek Time/Latency

Both CDs and DVDs tend to have a very high seek time and latency.

Seek Time/Latency

Blu-ray discs still have a fast seek time and latency, but not as high as CDs and DVDs.

Average Cost

Generally, both hard disk drives and magnetic storage drives have a high seek time and latency.

Storage Capacity

Magnetic tape

Generally, CDs, DVDs and blu-ray disc tend not to cost very much, for instance, (at tesco) 25 blank DVDs cost £8 (£0.32 per disc) and 100 blank CDs cost £14 (£0.14 per disc)

Hard disk

CDs tend to store the least amount of data at around 650 to 900MB,

A magnetic tape drive can generally store up to around 2 to 2.5TB of data.

Blu-ray discs cost a bit more at around £20 for 20 discs, however, as with most things, prices will vary

Most commercially sold hard disks store up to around 1 TB (terabyte) of data, however this size con range all the way up to 10 TB.

DVDs store from around 4.7 to about 9.4GB,

And Blu-ray discs store the most at anywhere between 25 to 128GB

Average Cost

Magnetic Tape

Hard Disk

Magnetic tape is one of the most cost effective methods of storing data

A 1TB hard disk costs around £52, which is around $0.04 per megabyte. This is a significant decrease from when they were first manufactured and sold

Optical Media

Magnetic Media

CDs, DVDs and Blu-ray

Hard disk drive and Magnetic tape drive

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General Information

Portability

All forms of optical discs are easy to transport as they are all quite small and thin. However you must keep them in a case as scratching the surface could corrupt the data stored on the disc.

General Information

Hard disks are not easily portable due to them being embedded in the computer, however external hard disks are available should you need them.

Optical media works by creating a disc with a pitted (not smooth) metallic surface. There are several different types of disk out there ranging from 650 MB to 128 GB, with the pits and lands getting closer together for higher volume disks. The principle behind how each of them works is the same.

Magnetic storage devices store data by give magnetic charge to a metal. The charges are then converted 1s and 0s and are able to be read and accessed.

Generally magnetic storage has been the most popular method storing programs and data, and making backups. However, solid state storage is beginning to be used more and more recently.

General Information

Storage Capacity

Similarly, SD cards can come in larger sizes such as 1TB or 512GB but smaller sizes are much more commonly used.

An SSD will generally have around half a TB storage capacity but drives with a full 1TB are available.

Flash drives can come in the same sizes as SSDs, but due to their portablity sizes of 16 - 32GB are more commonly bought.

Solid state devices have no moving parts, they are made with memory cards made up of semi conductors. Because of this they are significantly more durable and faster than magnetic and optical storage media

Solid State Memory

Solid State Drives, USB Flash Drives and SD Cards

Seek Time/ Latency

Due to the lack of moving parts, all forms of solid state memory have low seek times and therefore latency, making them the fastest secondary storage devices.

Portability

As with HDDs, portable SSDs are available should you need to store that much on the go, otherwise the drive is held in the computer.

The small size of both flash drives and SD cards, however, makes them much more easily portable than SSDs.

Average Cost

An average SSD will cost around £0.07 per GB of storage, this is around 67% higher than the cost of an equivalent HDD.

A flash drive generally costs anywhere from £3 - £75 depending on the storage capacity, an SD card is around the same price.