This applies a basic structure to the drive that the operating system can use to store data.
Some are platform-specific, including the default file system format for both Windows and Mac OS.
At least in Windows, the default value is 4KB for most drives.
But you’re free to manually change that, higher and lower, if you prefer.
The real question is, should you?
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What Is An Allocation Unit?
Storage drives are split into much smaller sections to make them more manageable.
Each of these sections is one allocation unit in size.
The allocation unit is the unit of file size on the drive.
No matter what size, every file will take up a perfect multiple of the allocation unit.
With the default 4KB allocation unit, all files will take up a multiple of 4KB on the drive.
Any space to the next multiple of 4KB file size is essentially wasted and unusable.
So why not set the allocation unit to be as small as possible?
Additionally, smaller allocation units increase the chance of fragmentation if youre using an HDD.
This will negatively impact HDD performance, which is significantly affected by non-sequential operations.
This specific effect will be much lower on SSDs that dont suffer a performance loss from fragmentation.
This means that the effect of large allocation units should be less of an issue on massive drives.
It also means that it should be less of a problem if youre primarily or exclusively storing large files.
If youve got a tremendous amount of storage space, closing space isnt much of an issue.
Interestingly, Windows allows for the drive size when suggesting the default allocation unit.Microsoft documentsthe actual figures here.
As 16TB drives are rare and excessively expensive, most people will only ever have seen this default value.
Only you’re free to say what key in of files youll store on your drive.
Youll likely have a mix of large and small files if its a general-purpose drive.
An allocation unit size of 4KB is generally considered optimal for most drives.
In Windowss default file format system, all drives below 16TB have a default allocation unit size of 4KB.
The allocation unit is the unit of storage a file can take up on the drive.
On average, half of the allocation unit is empty for every file on the drive.
Decreasing the allocation unit size increases the complexity of managing the file system as it results in more units.
Doing can also impact HDDs performance because it can result in increased fragmentation.
The size can improve performance slightly but also result in more space being lost per file.
