3.4 Backup media
Depending on the amount of data you need to backup, a range of technologies are available:
Optical storage is the same technology used for CDs, DVDs and Blu-Ray.
The most common technology for optical storage is writeable DVD standards including DVD-R, DVD+R, DVD-RW, DVD+RW and DVD-RAM. Most of these DVD formats can store 4.7 GB on a single disc, although newer, so-called, dual layer discs and drives can store twice that. Blu-Ray technology offers 25 GB and dual layer (50GB) formats with three layer 100GB discs, although they are expensive.
- Optical drives and media are extremely cheap and widespread. Most computers have an optical drive or can accept a USB driver and the discs can be bought in supermarkets.
- There are a large number of manufacturers, so there should be no problem with future supplies of discs.
- More modern optical disc technologies (such as Blu-Ray) also support most older types of disc such as DVD and CD.
- The media is relatively small. Large amounts of data can be stored in a very small space.
- The media is robust. Discs can be posted and are able to survive regular use or being dropped. They are resistant to extremes of temperature and humidity, and immune to strong magnetic fields.
- Optical drives are relatively slow compared to hard disks, especially when writing data.
- There are a large number of types of disc (especially recordable DVDs). Some of these discs are not widely supported.
- Their capacity is relatively low compared to hard disks. A 1TB hard disk is commonplace on modern computers, so it would take more than 200 DVDs to make a complete backup of the disk. Consequently, DVDs might be best suited to making backups of key data.
The magnetic hard disk at the heart of most computers can also be used as a backup device. Most PCs have sufficient internal space for a second hard disk that can be devoted to backups, or a relatively cheap external hard disk can be connected to a USB or Firewire port on a computer.
More expensive disks can be connected directly to a network using Ethernet or wi-fi in which case they are known as Network-Attached Storage (NAS). Disks can be made more resilient to failure by combining several disks together with copies of data stored on multiple disks so that even if one copy is damaged or the disk fails, it is not lost forever; the most common type of this ‘redundant’ storage is called a Redundant Array of Independent Disks (RAID).
- Disks are relatively cheap and capacities are growing rapidly.
- External hard disks can be easily moved between computers.
- There are many disk manufacturers, all of whose products can be used in almost any computer.
- There are a large number of backup programs designed to be used with hard disks. Many external disks are sold with applications to ease the backup process, or offer a ‘one touch’ backup button.
- Hard disks are fragile and easily damaged if dropped or exposed to extremely high temperatures or magnetic fields.
- If hard disks are used once to make a backup then archived, the replacement cost is much higher than for tape or optical media.
Solid State Disks
Solid State Disks (SSDs) are storage devices that can store data in memory chips without the need for a power source. The name is somewhat misleading because these devices don’t actually contain physical disks. They can be commonly found in the USB memory sticks used for sharing files between computers. As the technology has advanced to increase the storage capacity of SSDs they are now being used in laptops and mobile devices as substitutes for magnetic disks.
SSDs have the same advantages as magnetic disks when compared to optical storage technologies. Some additional advantages are:
- SSDs are more robust and are unlikely to be damaged if dropped or exposed to magnetic fields.
- It is possible to read and write data from SSDs much faster.
- There is no noise produced when SSDs operate because they have no moving parts.
- SSDs are more expensive than equivalent capacity magnetic disks.
- At the moment, the maximum capacity of SSDs available on the market is 1TB although this will increase as the technology advances.
Next, you’ll learn about remote backups.