What is an HDD and how does it work?
Hard disk drives (HDDs), also known as mechanical hard drives, are large-capacity memory devices. They consist of information storage units built from a set of mechanical parts in its interior and a set of magnetic disks.
The disks spin at high speed on the same axis, allowing read/write heads to read or write the data by magnetizing the surface. Compared to other types of storage devices, its main advantage is that they offer a high capacity on which to store information for a much-reduced price.
Advantages and Disadvantages of HDDs
The many advantages of mechanical hard drives help their popularity. They offer a large storage capacity at a much more affordable price. Additionally, they allow for an unlimited number of rewrites. On the other hand, their reading and writing speed is much lower.
- Large storage capacity
- Easier to recover lost data
- Unlimited number of disk rewrites
- Reduced read and write data speeds
- Susceptible to mechanical breakdowns if mishandled
Shopping Criteria for HDDs
When it comes to buying an HDD, it is important to consider some criteria regarding expert opinions. To help you in the selection process, we have chosen the ones we consider most important. We expect them to guide your purchase as much as possible to fit your quality-to-value ratio in the best way possible.
- Storage capacity
- Read/write speed
- Rotation speed
- Connection bus
Regarding tech experts’ opinions, when buying a mechanical hard drive, the first thing you have to think about is your intended use and with which device you are going to use it. You will not need the same type of HDD on a laptop as on a desktop computer. So, for a laptop, you will be interested in a disk size of 2.5 inches instead of the traditional 3.5 inches.
Also, is the computer you use for basic tasks, more professional use, or for playing video games? In each case, there will be a more specific type of hard disk geared toward each intention. It is even possible that you combine an SSD with an HDD to take advantage of the benefits of each.
No doubt, storage capacity is an important issue when buying a hard drive. However, do not let yourself be guided by this alone. Today, mechanical hard drives offer more than enough capabilities to meet the users’ needs.
Currently, there are HDD units with capacities ranging from 500 GB to 12 TB. For the average user, a 1 TB disk is more than enough. If you are going to use your computer for video games, a combination of a 250 GB SSD and 2+ TB on an HDD disc may better suit you.
Did you know that the very first hard drive, the IBM 350 Disk Storage Unit, was released in September 1956 as part of a complete IBM computer system?
Read/write speed is a fundamental aspect of an HDDs performance. However, it is often not given all the importance it deserves. A higher reading speed will allow the computer to boot much faster if the operating system is installed on that hard disk.
Similarly, it can also influence the performance of installed programs and applications. When playing video games, it will not decide performance, but it will reduce loading times.
In HDD devices, read/write speed will depend to a large extent on the disc’s rotation speed, which is measured in revolutions per minute (RPM). Currently, it is usual to find devices with speeds of 5400 and 7200 RPM, although there are some that reach 10000 RPM.
For a desktop computer, if you want to enjoy good performance, go for a disk with at least 7200 RPM. However, for laptops, the most common speed is 5400 RPM due to limitations derived from the smaller size of the 2.5-inch disks.
Hard drives have two memory areas. In one of them, data is saved even when there is no electric current. This is the main area and where files are stored. The other one is the cache memory, where information is temporarily stored when the disk receives an electrical current.
The cache allows the hard drive to access information faster. This is because every time the disk reads a piece of information, it leaves part of it stored in the cache. The most common is usually 64 MB. Logically, the larger it is, the faster the disk will find more data.
Currently, hard drives can use different interfaces to connect to the motherboard. The main ones are SATA, IDE, SAS, or SCSI. No doubt, the SATA standard is the most used by nearly all desktops and all the latest-generation laptops.
Current HDD hard drives are connected using the SATA III standard. This reaches a link speed of 6 GBps, resulting in 750 MBps of theoretical maximum transfer rate. However, at a practical level, this is reduced to 600 MBps.
There are many manufacturers of HDD storage units, but not all of them offer the same level of quality. Some of the most reputable brands include Toshiba, HGST, TrekStor, Seagate, Western Digital, and ExcelStor.
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What are the components of an HDD?
A mechanical hard disk consists of one or more plates, which are aluminum or glass discs. These disks rotate simultaneously on the same axis. Each disk has two faces: The head is the read/write device and is just a set of vertically aligned arms.
Read/write heads are at the tip of the arms. In total, each face requires one head. In addition, HDD disks also have an electromagnetic system and a board with a printed circuit that controls the disc. Finally, this whole set is covered by protective hardware.
How does an HDD work?
In mechanical hard drives, the plates are constantly spinning. This means that transfer times are reduced. Thus, when the operating system requests to read a file, the hard disk determines which disk and track it is in and moves the reading head there.
Data recording is carried out through electric current pulses by a device located in the magnetic head. These data are recorded on the magnetic surface in circumferences lines. When one is completed, the head moves to write a new concentric circumference.
What are the differences between a hard disk drive and an SSD?
For some years now, SSDs have been available on the market. These store information in flash memories connected to each other. Since they do not have mechanical parts, they reach read and write speeds much higher compared to those offered by external hard drives.
Other advantages include lower energy consumption and quieter operation. However, as it is a relatively new technology, it still has some drawbacks (such as a higher cost per gigabyte) than traditional hard drives
Are SSD units prone to breaking down? They don’t have mechanical parts and so are not prone to breaking down
Noise: Another advantage of the absence of mechanical parts is that they are less noisy, use less energy, and overheat less frequently than HDDs
Storage: Less storage capacity
Reading speed: Superior read/write speed; ideal for operating system installation
Rewriting: Can only rewrite a set number of times. However, most users will not exceed this amount
Price: Although the price has come down substantially, its price per gigabyte is much higher than that of HDDs
Are HHDs prone to breaking down? They can suffer breakdowns after harsh impacts
Noise: Can be noisy as the disks are spinning constantly and therefore can heat up quickly, thus consuming more energy
Storage: Offer the most storage capacity
Reading speed: Don’t reach as high read/write speeds, especially with large files
Rewriting: Can rewrite an unlimited number of times
Price: Much lower price per gigabyte
Is it worth buying a hard disk drive?
Today, the answer is yes, without a doubt. Even if you choose to install an SSD, it never hurts to have a secondary HDD for more storage. Since their price is so low, they do not require a large economic investment.
Who is recommended to buy an HDD?
If you have a computer—portable or desktop—you need a hard drive. Unless you require a reduced storage capacity or have an unlimited budget, you will have to go for a mechanical hard drive, either as a main or secondary unit.
Generally, in the opinion of an average user who does not need very high-performance equipment, an HDD is the best option. Not surprisingly, its value for money is excellent. Something similar happens if you need a large storage capacity, such as video surveillance systems.
What sizes of HDD exist?
Hard disk boxes mainly come in two sizes: 2.5″ and 3.5″. The first is used by laptops or consoles. Desktop computers, on the other hand, usually have installed 3.5″ disks. Keep in mind that size not only influences the space occupied by the unit, but it also determines its performance.
2.5-inch hard disk
Use: Used in portable devices and gaming consoles
Storage: Less storage capacity and slower speed of rotation; generally run at 5400 RPM
Memory cache: Smaller memory cache
3.5-inch hard disk
Use: Used in desktop PCs
Storage: Much higher storage capacity and faster rotation speed; usually 7200 RPM
Memory cache: Greater memory cache
What is the origin of hard disk drives?
Its origin tracks back to the 1950s when the American company IBM created the first mechanical hard disk. At that time, the first device of this type had a storage capacity of 5 MB. Its development allowed it to replace magnetic tape units, which were slower.
That first hard disk weighed a ton and was larger than a refrigerator. Since then, the technology of these devices has evolved to allow for greater capacities in smaller spaces. In 1992, capacities of 250 MB were reached, which became 40 GB in 2002, and currently exceed tens of TB.