Why are Hard Drives so slow at loading anything compared to SSDs

Hard Drives are slow for anything we want to do, specially loading any Operating System such as Windows; This slow speed can also cause some instabilities in the desktop environment. But why is that?

Well… Hard Drives contain a few platters and an arm. the arm moves on the platters and writes data to it or reads data off it. The arm has to move back and forth every fraction of a second which increases latency and that decreases data transfer speeds.

Here is how the arm moves on the platters: (the movement is slowed by 40x)
hard drive function in slowmotion
credit to The Slow Mo Guys on YouTube.
So when we want to load an OS, a game or watch a movie, the arm has to read the data off the platters and that’s why it takes a while .

On the other side, we have SSDs (Solid State Drives) which don’t have an arm to move around platters; instead, they have NVMs (Non Volatile Memories) and a controller to go over them which are much faster and more reliable(depends on the environment temperature).
NVMs are NAND based and NAND includes lots of transistors which store data in them with electrical charge. So, if we want to access data on an SSD, It would take a fraction of a fraction of a second! Here is some evidence to prove it:

All of that takes place in Random Access speeds;
Where a 7200 RPM Hard Drive has the speed of:

how slow an hdd is in random access

And an SSD has the speed of:
how fast an ssd can be in random access
SSD has a lot more In and Outs per second and the access time is almost negligible.
If you’re not convinced by the test results of the HDTune software, let’s look at a Real Life impact:

Let’s say we want to copy a Windows System32 files which contains a lot of small files such as DLL files to a Hard Drive, There will be a lot of speed bumps and hanging on one file compared to an SSD.
Here is copying the folder to a Hard Drive:
hard drive random file test
Here is copying the folder to an SSD:
ssd random file test

Although they look the same; but in loading any operating systems, Hard Drives might get so slow to the point where they become useless.

Well, there is a solutions to this problem with Hard Drives; files we copy to a hard drive, continue to Fragmentalize in platters and you can Defrag them by using tools related to this problem like the “Windows Defragment” tool; which you can access by going to your hard drive’s properties, in the tools tab.

windows defragment tool

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