A hard-drive or a hard-disk is also known as the secondary memory of computers or also secondary storage devices. Unlike RAM, hard-disks are designed to store data even if a computer is switched OFF ,i.e., storing data permanently. But if the hard-disk gets damaged (considering both physical and electrical damages) data can be lost over-time.
Today's hard-drive technology goes by the two different techs known as Hard Disk Drives abbreviated as HDDs and Solid State Drives known as SSDs. Most commonly used tech is HDD but it is being replaced by SSD. Hard-disks store all the data, Operating systems (windows, mac, etc.) music, videos, games, etc. To process these files, RAM loads them into their memories so that processor can process and execute them.
These images i have shown, shows both the technologies, that how do these look like from the inside of their cases. HDDs stores data magnetically on the disk also known as
platter. This platter stores data magnetically in the form of 0s and 1s. This data is written on the platter with the help of an arm which can be seen in this figure. The platter rotates about an axis passing through its centre and the arm can move from the circumference to its centre (if approachable). Data is stored in HDDs in sectors ,i.e., in parts. Storing data in HDDs can lead to data getting scrambled all over the disk which is also known as fragmentation. Hence it would be good to defrag the drive to maintain speed and health of the drive. SSDs don't require any such processes because data is directly stored without any problems.
This process of storing and reading on a HDD is overall time taking and so HDDs are considerably slower and their speeds are in MBps. Hence here comes the new tech known as SSDs. These SSD stores data in their CHIPS. Their is no such considerable delay in storing or accessing data from SSDs. Hence their speeds are in GBps which is a lot faster than HDDs. It can be seen that computers using SSDs to store their files to boot (storing their operating systems is SSDs) boot-up (start) in few seconds where as computers using HDDs can take minutes to load-up.
Hence SSDs are better option to choose while purchasing or building a computer but there are certain limitations of SSDs. These are:-
1. SSDs are much costlier than HDDs so if anyone is purchasing or building a PC/laptop, HDD would be a better option to them.
2. Life of SSDs is less considering to HDDs because writing, erasing then again writing leads damage every time it is done. But still there are researches going on and different algorithms/programs being made to reduce as such damage and so, SSDs can last upto a lifetime similar to HDDs.