Once we are aware that there are different types of storage device, we also need to be aware of the different characteristics of storage types to allow us to identify the most appropriate storage for a given scenario.
Not all storage is made in the same way, and because we demand the ability to access our data in different ways, a range of storage solutions needed to be developed.
The one thing to remember for secondary storage is that it is all non-volatile – that is, when the power is switched off, the data is retained.
There are six main characteristics that we can consider when looking at different types of data. For this, we are going to consider just two scenarios – backing up a whole computer system & moving a file containing homework from home to school:
Capacity
Capacity relates to the volume of data that can be stored on a device. In some circumstances, it is important to have a large capacity.
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| Large capacity needed to store all files | Small capacity needed to store one file |
Speed
When we discuss speed of a storage device, we are referring to how quickly the computer can read and write data to and from the device. This is often dependent on whether the device contains moving parts.
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| Fast speed may be useful if backups are taken when people need to use the system | Because files are small, the speed of the device isn’t always relevant |
Portability
Portability is often an important factor for storage devices as we use more devices that move around with us. Characteristics of a portable device are being lightweight and small – imagine a smartphone with a full sized hard drive!
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| If the backup is being moved off-site, then the device will need an element of portability | Moving a file to school means that the device must be small & light enough to easily carry around |
Durability
If something is durable, that means that it can withstand physical movement or even being dropped. Devices that need to be transported between locations regularly need to be durable to prevent them from being easily damaged.
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| Durability is less important for backup devices as they are not carried around regularly | If the device needs to be transported back & forth to school, being durable is important |
Reliability
It’s easy to confuse durability and reliability, but reliability refers to whether a device can be relied upon to work time and time again. If the device fails, how much of a disaster would it be?
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| If a backup device fails and the main system needed to be fixed, important data may be lost forever | Because the file is being moved using this device, if it fails there will be another copy. Reliability is useful, but not critical |
Cost
The cost of storage can be looked at in several ways. We can measure cost per MB, or the cost of the device as a whole. Sometimes, although the cost per MB may be higher, the capacity needs are smaller making the cost per device more important – e.g. CDs & DVDs
| Whole Computer Backup | Moving Homework File To School |
|---|---|
| Backup devices would be measured by cost per MB as the need for capacity is important | Devices for transferring files would be measured by cost per device as the need for capacity is low |
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