Why is HDD 100% loaded?

Question

Hard disks

Input data:
8 identical stationary computers (completely identical)
Everywhere is WIndows 10 and HDD Toshiba DT01ACA050 on 1TB
And at all stations the HDD is 100% loaded with standard Windows services, permanently
I change to SSD and everything is in order.
What could be the problem? Also on new laptops there is a similar problem.
CrystalDisk shows a good state of disks, there are no bad sectors.

Answer 1

Why is HDD 100% loaded?

Because it has a system.
Do not put a system on it and there will be no problem.
The system constantly writes and reads from the system disk, and the volume of reads and writes is scanty, and the number of reads and writes is huge.
The speed of an average HDD on linear reading is around 150 megabytes per second.
The speed of an average HDD on random reading in small blocks is around 0.5-0.9 megabytes per second.
The average SSD provides random reading in small blocks of 10-20 megabytes per second.
10-40 times more than HDD.

Answer 2

The random access speed of the HDD is low. And the system consists of many small files. Windows 10 even more so. In the current realities, without an SSD, under the system disk, we get a brake computer.

Answer 3

See who writes to the disk the most and kill this process. If possible, get a brick before reboot. Why M$ does not live in the cache for these needs - xs.