If you have noticed the hard disk and if you noticed the CD then you would have realised that up to thousands of times the amount of data which can be stored in a CD can be stored in a hard disk and already a CD is very compact while the hard disk is larger in size than a CD but still it is very compact and portable hard disk are also very small as well.
That is why over the years the CD’s have become less relevant and there has been a rise in the usage of portable hard disk.
The question which arises is that how can so much amount of data can be stored in such a small hard disk?
Over the years is the capacity of the processor has increased the speed at which you can to try and write the data into the hard disk has also increased and therefore the capacity of hard disk is also increased but the question which arises is the same all the time how is it possible to store so much of data in such a small hard disk?
Principle of magnetism:
In order to understand the principle of magnetism we have to look at the basic concepts which were taught to us in schools. You might have already experimented with the principle of magnetism in your school and the experiment goes like this:
When you have group of nails and if you have a very powerful magnet and if you move it over the nails then you would understand that the nails also get magnetised and stick to each other and they remain in that position for quite some period of time unless and until an external force is disturbing them.
Therefore this simply means that the magnetic energy from the back and it was transferred into the nails for a limited period of time and while this energy is pretty weak but it illustrates an important example that magnetism can be transferred for a small period of time.
Magnetism can be used to pass on coded messages as well because when you magnetise and nail then you can easily pass it on to someone else who can check whether the nail has been magnetised are not by just simply placing a paperclip near to that nail and if the paperclip sticks to that nail than that simply means that the nail has been magnetised and the principle can be used to pass on coded messages as well where the magnetism of the nail indicates a certain message and the unmagnetised nail if given to that person indicates the opposite message and therefore information can easily be passed with the help of the indication of magnetism.
A single nail can contain an affirmative order negative message according to our about example and that means that the nail actually contains one bit message. The computers and every other technology also works in the binary mode which contains only two digits that is 0 or 1 and therefore this single bit message 0 or 1 can help you in storing the data as well. The example of an magnetised nail storing one bit of information is just an example to explain the entire process of magnetism.
Let us take our analogy of an magnetised nail storing one bit of information a bit further and let say you have a hard disk containing a capacity of 20 GB. Then the amount of information which can be put into that hard disk is equivalent to the information which can be contained by 1.6 million nails. That is you can also say that the amount of information which can be put into that hard disk is 1.6 million bits.
How does a hard drive work?
If you have looked at the internal side of the hardest then you would have noticed that it contains of a circular plate on which there is always a pointer and this point and actually writes the information or reads the information from the circular plate and the information which is stored is stored with the help of magnetism and this plate which you see is divided into billions of small areas which can be either magnetised or the magnetised and the status of these billions of areas determines the information which is stored in the hard disk because when the area or the cell is magnetised you can say that it stores of 1.
Similarly, if the area is the demagnetised then it stores is 0. A series of these 1s and 0s that determines the information which is stored.
For example, if seven adjacent cells have the bits 1111111 and if another seven cells have the bits 0011001, then both of these set of cells have completely different information from each other and this information can be read with the help of the binary number system.
Parts of a hard disk:
When you open the hard disk you would see a actual assembly and not just the magnetic plate. Below we would be explaining all of those parts and what is the function of those parts.
1. Actuator: This is the part of the hard disk which holds the reading and writing arm in place and this part is also responsible for moving the reading and writing arm. In earlier hard disk which are more mechanical parts this part was actually a stepper motor whereas these days it is a voice coil. A voice coil is much more precise and works like an electromagnet to move the reading and writing arm at a very high speed and therefore the reading and writing speeds of the hard disk have actually increased over the years.
2. Reading and writing Arm: as the name suggest more is across the magnetic plate to read or write the data.
3. Central Spindle: This is the part of the hard disk which holds the magnetic plate in place when it is being rotated to read or write the data.
4. Magnetic Plate: This is the magnetic plate as we have explained above which is divided into billions of tiny areas to store the information with the help of magnetism.
5. Connector Slot: This is to connect the hardest to the assembly in the central processing unit or to connect the hardest to the computer with the help of a USB slot.
6. Magnet on the read and write arm: This is the magnet which is actually used for magnetising or the magnetising the billions of areas on the magnetic plate and it is at the end of the reading and writing arm, directly in contact with the magnetic plate.
7. Circuit board: This is the circuit board which controls the flow of data from and to the magnetic plate.
8. Connector: This is the connector which is inside the hard disk and it is flexible to move during the reading and writing of the data on the magnetic plate.
9. Spindle: This is spindle along the reading and writing arm to move across the magnetic plate quite easily.
These are the parts of a hard disk which enable it to read or write data at high speed.
As you can see from the entire assembly the magnetic plate is the most important part of the hard drive and that is where the information is stored as well and this magnetic drive is actually made from glass or aluminium but for the actual magnetism to take place it is coated with a layer of metal.
If you look at the entire assembly which we have mentioned about it would contain only a single metal plate but in hard drives of larger capacity that can be more than one metal plate as well to store more data.
What our diagram does not show is that there are actually two reading and writing arm is which continuously read the information from the hard disk and one is a buoyant and one is below it this is done to increase the speed of reading and writing although these arms read the information from the magnetic plate at a very high speed because the magnetic plate has the capacity of rotating up to 10,000 revolutions per minute.
To minimise the wear and tear and to increase the life of the hard drive there is a small fluid between the actual magnetic plate and the reading and writing arm magnet and therefore they are not in direct touch with each other but with the help of the fluid.
Reading and writing cycles on the hard drive:
The main purpose of a hard drive is to store information but the information also would be drive able as well because if you’re not able to retrieve the information act will then there is no point in storing the information in the hard drive.
For storing the information in the hard drive there is a specific process because the information is stored in a proper orderly manner and not in a haphazardly manner because if the information is stored in a haphazard manner then it would not be easily do drive able when you’re trying to retrieve the information.
The magnetic plate which you saw above stores the information and concentrate circles known as tracks and these tracks are further divided into small sectors and this information is available easily to the machine which is trying to extract the information from the magnetic plate.
Whenever you are saving some information you would realise that it gets saved continuously and that means that it is being saved and adjacent sectors on the hard disk as long as you have given the command to save all the information at a single destination drive. All of this information is available in a map known as the file allocation table and some of you might have already seen it in the computers as well by the name of a FAT.
This file allocation table enables the computer to know which sectors are free for saving the information and which sectors have already been used up and therefore when you give the command of saving some date are the next time around the reading and writing arm automatically most of the sectors which are present and allocated to that particular destination and are already free and no information has been saved in them prior to this.
Reading the information it is the same process but in reverse.
How safe is a hard disk?
From the working of the hard disk or the hard drive you might already realise that it is a great piece of engineering and it is a very sophisticated method of working but how safe is the hard drive.
You would save all the data in a hard drive thinking that it is safe but the question which arises is that candidate be lost from the hard drive. The answer to that question is yes.
Hard drives are susceptible to dust and dirt and other contaminants because if it settles on the magnetic plate then the reading and writing arm which is moving at the very rapid pace as we explained about up to speed of 10,000 rpm can be unsettled and can move up and down due to this disturbance on the surface of the magnetic plate and therefore it would crash into the magnetic plate as well as the outer covering of the hard disk and therefore damaging the entire magnetic plate and the loss of information can be drastic because you cannot predict this and whenever this happens all the data on the hard disk is lost.
This generally occurs suddenly and therefore the only option which you have got to keep your data safe is to ensure that you always have a backup.