Storage devices, such as hard disk drives and USB flash drives, are used to store application and user data. This storage is persistent, it doesn’t forget the data it is storing even when the computer is turned off.
As well as the store our files and application on our device so we can use them, storage is also important for backup and recovery, should our data be harmed. There are a number of technologies that are particularly useful for this.
In this lesson, we’ll learn about:
As mentioned in the lesson introduction, storage devices are used to store application and user data. These can be internal which will be used to hold data for the running of the computer, or external which are useful for transferring files to other devices, as well as for backup.
Some example storage devices include:
These are commonly used as the primary storage devices in a computer system, particularly servers and desktop computers. It can be used as an external portable storage device too, but it isn’t as ideal for this as other options.
HDDs (Hard Disk Drives) are a form of magnetic storage. They consist of a number of disks made of magnetic material that we call platters. The hard disk drive magnetises and demagnetises billions of tiny individual areas on the platter.
Because computers store all data in 1’s or 0’s (known as binary), we can store our data this way as a magnetised area represents a 1 and a demagnetised area represents a 0.
These are used often as a portable storage device with a large capacity. However, they are also commonly used as the primary storage device in laptops and recently in desktop computers.
SSDs (Solid State Drives) are a form of flash memory storage. They store data using semiconductor chips. These chips can be switched to either an “on” or “off” state. The “on” state representing a 1 and the “off” state representing a 0.
SD Cards and USB flash drives are additional forms of flash memory storage. These are specially designed as external portable storage devices though as they are very small and light-weight.
As they are so much smaller than SSDs they will not offer as much storage/will be more expensive for similar levels of storage.
CDs, DVDs and Blu-Ray disks, are all examples of optical disks. They’re most commonly used for storing music, films, tv & software, for distribution by suppliers (i.e. game publishers distribute games on disk to retail stores to sell).
All of these different types of disk are a form of optical storage. This works by using a laser to mark the disks in a pattern. A light is then bounced off the disk and is read back differently depending on whether the light bounces off a marked or non-marked area. Marked areas are known as “pits” and represent 0’s in binary, non-marked areas are known as “lands” and represent 1’s in binary.
We mention SD cards and USB flash drives are forms of flash storage. When would you use these storage devices instead of an SSD?
There are a number of technologies used with data storage to help protect data from harm and help us to recover damaged data. Two of these technologies we’ll look at now.
Redundant Array of Independent Disks is a technology used to store data in multiple locations across separate disks. These disks will appear as a single logical disk in your OS. This will be able to provide data redundancy to protect data as well as to provide performance improvements.
There are different RAID levels that provide different benefits. For the most part, these different levels use two main techniques, disk striping & disk mirroring.
Network Attached Storage is a device that we can connect to a network that allows us to access our files from a central location. So we can store our data on the NAS device instead of/as well as on our computer system. It is essentially a very simple file server.
NAS devices are very useful for sharing files between multiple users so we can work collaboratively on these files. It also allows us to work on different devices on the network and still have access to our data.
NAS is also popular for backup and recovery purposes. We can automate backups of our data to the NAS device so that if something happens to our computer or the data on it, we can recover from the backup.
We mentioned above that there are different levels of RAID. Research about these levels and the differences between them.
So to summarise what we’ve learnt in this lesson: