What are the different types of hard drives?
All computers and servers are equipped with hard drives, but they are not all identical.
On the market, the main storage options are:
- Hard Drives (HDD)
- Solid State Drives (SSD)
- Solid State Hard Drive (SSHD)
Hard Drives are the most often used as they are easy to buy and use. They have a minimal cost and can bear a high storage capacity : one terabyte costs almost nothing. However, the biggest problem of this drive is its slowness.
As you might know, Hard Drives are actually composed of a disk rotating on itself at the speed of 5400 or 7200 turns per minute depending on the model, and a single head. Since there is only one head that has to read everything, the HDD reacts badly when it has to manage several file transfers at the same time (it cannot do two operations or more at the same time) and slows down. Furthermore, since the head will be used frequently during a disk’s lifetime, it will inevitably wear off and the HDD will break. To speed up a bit an HDD, you must defragment its files, meaning you have to align all the files’ data for them to be physically contiguous.
SSDs are the costliest solution. Their price is fixed with the number of gigabytes of data they can store, which make them quite onerous. Usually, computer manufacturers will hesitate to include an SSD in their products. We can find 120 GB SSD, which is about 11% of the capacity of a HDD.
It is however currently the fastest disk on the market as its data is stored on small electrically charged cells, and can do many operations at the same time (read/write or transfer).
Compared to a HDD where only physical maintenance may be needed, the SSD needs to be trimeed by the OS, so that files that have been deleted will be marked as overwritable on it (it does not detect them automatically).
SSHDs are hybrid disks combining the two technologies : the disk is separated in two halves, one SSD part where all the most often used files are saved and one HDD part.
It faces both the HDD and SSD problems : you must defragment and trim the SSHD regularly. However, it has a huge capacity and speed combined. The SSHD price varies between the HDD and SSD and it processes operations faster than the HDD if you do not fill its space completely.
The SSD is the fastest but the costliest, while the HDD is the cheapest and the slowest. The SSHD is also fast as long as you don’t use its storage completely. Depending on your needs, think well and choose what option you need between SSD, HDD and SSHD.
Published by Rémy Samkocwa, translated by Hugo Warin, corrected by Luka Lafaye de Micheaux