If you dont know, then this post offered by MiniTool will tell you answers.
Have you ever tried toformat your hard driveor USB flash drive?
If you have, then you might have noticed theAllocation unit sizesetting.

But do you know what allocation unit size means and should you reset it?
And if you want to reset it, then what allocation unit size should you use?
The answers are shown below, so keep reading.
What Does the Allocation Unit Size Mean?
First of all, what is allocation unit size?
it’s possible for you to see the Allocation unit size prefs when you format your hard drives.
It can also be called cluster size and it is the smallest possible chunk of data on your drive.
What Allocation Unit Size Should You Use?
What allocation unit size should I use?
You may ask yourself.
For example, Microsoft provides a list of default sizes for various versions of Windows on its website.
Usually, using the system default is the best choice, but this is not always the case.
For everyday calculations, this is not suitable.
Using a larger size than the necessary allocation unit can cause unnecessary fragmentation on the drive.
In most cases, Microsoft recommends an allocation unit size of 4 KB.
This is what the company says is best for standard users.
If you want to change the default size, then you should already know why to modify it.
Should You Use Different Sizes for SSDs or Hard Drives?
You may also want to know whether you should use different sizes for SSDs or hard drives.
As mentioned above, fragmentation does not cause the same problems on solid-state drives as hard drives.
But does this actually speed things up?
The answer may be no.
Some examples we have already seen in standard hard drives also apply here.
Even then, you are unlikely to see any measurable performance difference.
Bottom Line
What does the allocation unit size mean?
After reading this post, you should have got the answer.
There are always exceptions, but this is usually the rule.