1.3 - Storage
In this section (click to jump):
What is storage?
This will never, ever, get old.
We need to always remember that all a computer is ever dealing with is a stream of binary data - 0's and 1's. When we talk about storage or memory, all we are really talking about is a place to put 0's and 1's! That's all it is.
Storage and Memory are often misunderstood and mixed up in exams. So what's the difference?
If you've been doing this in order, or are already something of a Computing Beard, you will know that Memory is:
You will also remember that if memory is temporary, this means it is volatile - meaning the contents is lost when the power is off.
Storage then, is:
Which, in simple terms, means this is the thing that holds all of your data, all of your applications and anything else you don't want to lose from one power cycle to another. This is the device that means you don't have to start from scratch every time you turn a machine on!
The difference, then, is that RAM (memory) is much smaller than storage and is volatile, but is much faster and therefore suitable as a working space. Exams often ask why we need storage if we have RAM or vice-versa and the answer is:
Storage and Memory are often misunderstood and mixed up in exams. So what's the difference?
If you've been doing this in order, or are already something of a Computing Beard, you will know that Memory is:
- A temporary working area for open, running programs and data.
You will also remember that if memory is temporary, this means it is volatile - meaning the contents is lost when the power is off.
Storage then, is:
- A device which provides mass, non-volatile, permanent storage for programs and data.
Which, in simple terms, means this is the thing that holds all of your data, all of your applications and anything else you don't want to lose from one power cycle to another. This is the device that means you don't have to start from scratch every time you turn a machine on!
The difference, then, is that RAM (memory) is much smaller than storage and is volatile, but is much faster and therefore suitable as a working space. Exams often ask why we need storage if we have RAM or vice-versa and the answer is:
- RAM is needed for speed - it enables the CPU to work quickly with programs and data
- RAM, however, is much smaller than storage and is volatile, meaning the contents is lost when the power is turned off...
- ...therefore we need storage to enable us to persistently store data and to enable the storage of large quantities of programs and data.
Storage Quantities
You have a womans purse! I'll wager that purse has never been used as a rowing boat...
So we know that storage is a place where we store 1's and 0's without losing them when the power is turned off. Next we need to make sure we understand how many of these 0's and 1's we can store on a particular device. You'll have heard the terms Gigabyte, Megabyte (especially when it comes to mobile phone contracts) but what do these actually mean? You should find the following list really easy to remember, especially as you only have to remember about 3 numbers. It works very much in the same way as grams, kilograms, tonnes etc.
First of all the smallest quantity we can store:
Then we start putting many bits together to make bigger quantities:
It shouldn't be too hard to spot the pattern and this is what makes it easy to remember. As soon as you know 8 bits = a byte, then every quantity after that is 1024 of the previous amount.
A couple of points:
First of all the smallest quantity we can store:
- a 0 or a 1 = a Bit
Then we start putting many bits together to make bigger quantities:
- 4 bits = a Nybble (no I didn't make it up.)
- 8 bits = a Byte
- 1024 Bytes = 1 Kilobyte (Kb)
- 1024 Kilobytes = 1 Megabyte (Mb)
- 1024 Megabytes = 1 Gigabyte (Gb)
- 1024 Gigabytes = 1 Terabyte (Tb)
It shouldn't be too hard to spot the pattern and this is what makes it easy to remember. As soon as you know 8 bits = a byte, then every quantity after that is 1024 of the previous amount.
A couple of points:
- Manufacturers of devices decided that 1000Mb = 1Gb. This goes some way to explaining why when you buy a 64gb Iphone, it doesn't actually have 64Gb of storage. This is because, regardless of how manufacturers measure storage, computers work in powers of 2 and will always measure using the quantities we just learned.
- You can use these measurements in the exam... but I wouldn't if I were you.
- You need to know how to convert between these quantities. For example, exam questions often ask things like "a computer has 1Tb of storage, how many bytes is this?" The answer is easy - 1024(bytes) * 1024(Mb) * 1024(Gb) * 1024(Tb) = 1,099,511,627,776 Bytes
Magnetic Storage
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Magnetic storage is as old as the hills. It's up there with the dinosaurs in technology terms, yet until very recently, its been seemingly impossible to move away from.
Magnetic storage first started out in the form of tapes - big old reel to reel things, then cassette tapes (which stopped the tape getting so easily damaged). These stuck around for decades before other forms of storage took over. In the 1990's you'd probably have listened to your music on a walkman which took cassette tapes, or if you were properly rich, you may have even had a mini disc player.
Magnetic storage first started out in the form of tapes - big old reel to reel things, then cassette tapes (which stopped the tape getting so easily damaged). These stuck around for decades before other forms of storage took over. In the 1990's you'd probably have listened to your music on a walkman which took cassette tapes, or if you were properly rich, you may have even had a mini disc player.
90 minutes of music and only takes 2 AA batteries. Crazy.
When computers became more mainstream, cassette tape was the obvious way to store programs and data - the technology was already in homes and, more importantly, it was really, really cheap. The only problem with it was speed - reading and writing data to tape is a slow, slow process.
Things moved on and machines started to come with floppy disk drives. These used similar technology - the disk had a magnetic coating which was used to store data. These had the advantage that they were slightly less bulky to store, could hold more data than a tape and were much, much faster to read and write.
Floppy disks stuck around for a phenomenal amount of time. They first appeared in the 1970's and weren't fully phased out until around 2010 - in technology terms this is the equivalent to about 3000 years.
The reason for this is that they offered a convenient way of moving data from one place to another - they were easy, very cheap removable storage. Until solid state storage (read more below) became much, much cheaper and USB memory sticks appeared there wasn't a convenient removable storage medium to replace floppy disks with.
Finally in our quick tour of magnetic storage - hard drives. These were a complete revelation - large amounts of storage fixed inside your computer that was not only non-volatile, but could be changed as well. This was a total game changer. Before Hard Drives, all software was stored on individual disks and every time you turned your computer on you had to load a program from disk, then maybe change the disk to load your work files, then swap the software disk back and so on. Having a hard drive meant that all of a sudden you could install your software and it would still be there when you turned the computer on again the next day - crazy stuff.
Things moved on and machines started to come with floppy disk drives. These used similar technology - the disk had a magnetic coating which was used to store data. These had the advantage that they were slightly less bulky to store, could hold more data than a tape and were much, much faster to read and write.
Floppy disks stuck around for a phenomenal amount of time. They first appeared in the 1970's and weren't fully phased out until around 2010 - in technology terms this is the equivalent to about 3000 years.
The reason for this is that they offered a convenient way of moving data from one place to another - they were easy, very cheap removable storage. Until solid state storage (read more below) became much, much cheaper and USB memory sticks appeared there wasn't a convenient removable storage medium to replace floppy disks with.
Finally in our quick tour of magnetic storage - hard drives. These were a complete revelation - large amounts of storage fixed inside your computer that was not only non-volatile, but could be changed as well. This was a total game changer. Before Hard Drives, all software was stored on individual disks and every time you turned your computer on you had to load a program from disk, then maybe change the disk to load your work files, then swap the software disk back and so on. Having a hard drive meant that all of a sudden you could install your software and it would still be there when you turned the computer on again the next day - crazy stuff.
Hard Disk drives consist of big shiny metal discs called platters. These platters are covered in an iron oxide coating, which as you should know from your science lessons is... Rust. But it's also really quite good for use in magnetic storage.
These platters spin round at high speed - 5200 - 7200 RPM and data is stored in circular tracks on the disk. To read and write the data, a mechanical arm sits at the side of the disk and moves a very small electromagnet "read/write head" over the surface.
Why am I telling you how they work? Because it really helps explain some of the advantages and disadvantages. Lets summarise:
Advantages:
Disadvantages:
These platters spin round at high speed - 5200 - 7200 RPM and data is stored in circular tracks on the disk. To read and write the data, a mechanical arm sits at the side of the disk and moves a very small electromagnet "read/write head" over the surface.
Why am I telling you how they work? Because it really helps explain some of the advantages and disadvantages. Lets summarise:
- Hard Drives are magnetic storage
- They store data on spinning discs called platters
- They provide large amounts of storage - 1TB at least, up to 8TB (or more in future) per drive.
Advantages:
- They are cheap. Absurdly cheap. At present they are the cheapest type of storage per GB available.
- They offer very high storage capacity - up to 8TB per drive
Disadvantages:
- Now we have SSD storage, Hard Drives are painfully slow in comparison. This is because it takes time to spin the disc, then get it to the correct position, move the read/write head etc. All these things slow them down.
- They have moving parts - this means they will eventually wear out.
- They can be badly damaged by shock, movement, drops etc. Again, this is because they have moving parts. If the read/write head touches the platter then data can be destroyed.
- They are large (compared to flash/SSD storage) and consume more power than solid state alternatives. This means they are not good choices for small or portable devices and anything that relies on battery power.
Optical Storage
Definition: Optical storage is storage which uses laser light, reflected off the surface of a suitable disc, to read and write data.
There are three main types of optical storage that you need to know about. You will also need to be able to remember the amount of storage each one provides (or at least in order of biggest to smallest). These are:
All of these optical storage types work in roughly the same way. The surface of the disc is made up of flat sections and pits. A laser light is reflected off the surface of the disc and depending on whether it hits a flat or a pit will result in a 0 or 1 being read from the disc. The difference between the three is the wavelength (think of it as thickness) of light used and how close together the tracks are. This can be seen in the diagram below:
There are three main types of optical storage that you need to know about. You will also need to be able to remember the amount of storage each one provides (or at least in order of biggest to smallest). These are:
- CD (700Mb)
- DVD (4.7Gb)
- Blu-Ray (25-50Gb)
All of these optical storage types work in roughly the same way. The surface of the disc is made up of flat sections and pits. A laser light is reflected off the surface of the disc and depending on whether it hits a flat or a pit will result in a 0 or 1 being read from the disc. The difference between the three is the wavelength (think of it as thickness) of light used and how close together the tracks are. This can be seen in the diagram below:
Optical storage is largely on the way out in computing these days as the storage capacities have been surpassed by more convenient methods of storage such as USB memory stick. Have a think now - can you remember the last time you even put a disc into a computer? Tablets don't have drives that accept them, this laptop I'm typing this on certainly doesn't have an optical drive, Apple ditched them years ago now and no one has really missed them. However, they are still used - especially to distribute software or video content in shops and even on the cover of magazines. They can also be used to transfer small amounts of data between machines - for example if you were sending some files to someone through the post maybe.
Advantages of Optical Storage:
Disadvantages:
Advantages of Optical Storage:
- Very, very cheap to produce (CD's and DVD's are throw away items, unfortunately)
- Reasonable amount of storage depending on medium used
- Can be useful where you need something relatively compact (i.e. to give away material or distribute data)
- Fairly robust as long as the surface is not badly scratched
- Removable so can be used for small amounts of data backup
Disadvantages:
- On writeable media (the ones you can burn yourself) the data may not last longer than a few years before becoming unreadable.
- Often size is a problem - 4.7Gb on a DVD can be too small, 25Gb Blu-Rays are more expensive and still may not be enough
- Not suitable for large scale back ups
- Can be easily scratched or damaged, even shattered if bent.
- Not all devices contain a drive capable of reading discs, or all types of discs
Solid State Storage
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Lets clear something up, this can also be called "flash" memory...!
Generally, when we talk about solid state storage we are talking about anything which uses flash memory chips to store data.
Flash memory is a special type of memory chip which is non-volatile, and we all know by now that means it will not lose the contents from one power cycle to another.
So, solid state storage is:
There are several different types or forms of solid state storage, these are:
They all have some really, really important advantages over most other types of storage:
There are always disadvantages:
Generally, when we talk about solid state storage we are talking about anything which uses flash memory chips to store data.
Flash memory is a special type of memory chip which is non-volatile, and we all know by now that means it will not lose the contents from one power cycle to another.
So, solid state storage is:
- Any storage device which uses non-volatile, flash memory chips to store large amounts of data.
There are several different types or forms of solid state storage, these are:
- Memory Cards (SD, CF)
- USB Memory Sticks
- Solid State Drives (SSD's)
- Internal device storage - e.g. the storage on your phone or tablet.
They all have some really, really important advantages over most other types of storage:
- Size - Flash is extremely small and so we can make very small devices with large amounts of storage
- Power - They use very little power and so are really suited to battery powered devices
- Speed - Flash is stupidly fast when compared with any other type of mass storage. They can significantly increase the speed of a computer and are often a great option for upgrading older hardware to make it more usable (classic exam question alert)
- Capacity - They are now available in large capacities, up to around 1Tb without prices being absurd
- Robustness - They do not have any moving parts and so are very, very robust - they are suitable for devices that may be moved, shocked or mistreated.
There are always disadvantages:
- Cost - they are still more expensive per Gb when compared to a traditional hard disk drive
- Longevity - they have a limited number of read/write cycles. What this basically means is you can use them to death - never rely on a USB memory stick as your only storage device, for example, because they will eventually begin to lose your data or not work at all.
Cloud Storage
"Cloud" doesn't seem such a glamourous, fluffy, wonderous term when you see what it looks like in reality...
"The Cloud" is a term that gets rolled out all the time, it sounds amazing, doesn't it? We are literally using fluffy clouds to make cool things happen! You can even store photographs in the sky, who thought it?
But we know better than that, right?
Where did the term come from? There are several possible explanations, but the most likely is that no one really knows what the internet looks like and often when you see diagrams of it, people literally just stick a cloud in the middle and write "internet" on it. Hang on and I'll google you an example...
But we know better than that, right?
Where did the term come from? There are several possible explanations, but the most likely is that no one really knows what the internet looks like and often when you see diagrams of it, people literally just stick a cloud in the middle and write "internet" on it. Hang on and I'll google you an example...
See! A Cloud!
So, if the cloud is just the internet, what is "cloud computing" or "cloud storage?"
The answer is:
Cloud Computing - Using computing power/time from somewhere else, connected through the internet.
Cloud Storage - Storing data on a computer connected to the internet. Usually this is in a data centre, owned by a large company such as Apple, Google, Facebook, Amazon.
Cloud storage is currently the "next big thing" and with good reason.
Advantages:
Disadvantages:
The answer is:
Cloud Computing - Using computing power/time from somewhere else, connected through the internet.
Cloud Storage - Storing data on a computer connected to the internet. Usually this is in a data centre, owned by a large company such as Apple, Google, Facebook, Amazon.
Cloud storage is currently the "next big thing" and with good reason.
Advantages:
- Cost - you do not need to buy servers, physical drives or more storage - just rent it from a cloud provider. This is a big deal as server equipment can be hugely expensive and cloud storage tends to be much cheaper.
- Maintenance - you do not need to worry about maintaining or upgrading your servers or storage
- Capacity - you can, in theory, rent as much storage space as you need. If your needs grow, you can just rent more space.
- Backup - organisations use cloud storage as backup, it's ideal as data is stored far away from the original (a good thing). It's also the case that you don't need to worry about the backup of your own data - the cloud company is responsible for looking after your data.
- Access - you can access your data from anywhere that has an internet connection, giving greater flexibility to you or your organisation.
Disadvantages:
- Cost - a provider could raise their costs at any time.
- Security - you are still responsible for the security of your data (data protection act) and as your data is in cloud storage... its connected to the internet, which means it could be vulnerable to hackers.
- Access - if your internet connection goes down or your cloud provider has technical difficulties, you cannot access your data.
The right tool for the job
In the exam you can be asked about any of the types of storage in pretty much any scenario. The answer to these questions should be really, really obvious, but they won't be if you don't know the following:
If you know your storage types then it becomes trivial to decide which one goes where. Lets look at some simple examples:
All of these examples use the advantages and disadvantages outlined on this page. If they look new to you... erm... you need to scroll up and try again!
- The definition of each type
- The typical capacity of each type
- The advantages and disadvantages
If you know your storage types then it becomes trivial to decide which one goes where. Lets look at some simple examples:
- A slim, ultra portable laptop - SSD. Why? Low power, very small physically.
- Backing up a server - Tape. Why? Standard method of backing up data, can be stored externally, robust. Cloud may be an alternative.
- Giving away some e-books on a magazine cover - CD. Why? Small amount of storage, very cheap, small.
- Storing TV programs in a set top box - HDD. Why? Cheap, huge amounts of storage (video is large), reliable, suitable for many read/write cycles
- Transferring pictures from one computer to another - Memory Stick or Memory Card. Why? Relatively large capacity, easily portable.
All of these examples use the advantages and disadvantages outlined on this page. If they look new to you... erm... you need to scroll up and try again!
