How to find Allocation Unit of your Disk Partition?

Default allocation unit of any disk partition under Windows operation system is 4096 bytes for drives under 16 TB, this is the information as per Microsoft article 140365. The allocation unit is also referred as Cluster size.

Simple and fastest way to check what is the allocation unit size of any partition is as follows:

Command:
C:\Windows\system32>fsutil fsinfo ntfsinfo C:

Output:
C:\Windows\system32>fsutil fsinfo ntfsinfo C:
NTFS Volume Serial Number : 0x0000000000000000
Version : 3.1
Number Sectors : 0x0000000000000000
Total Clusters : 0x0000000000000000
Free Clusters : 0x0000000000000000
Total Reserved : 0x0000000000000000
Bytes Per Sector : 512
Bytes Per Cluster : 4096
Bytes Per FileRecord Segment : 1024
Clusters Per FileRecord Segment : 0
Mft Valid Data Length : 0x0000000000000000
Mft Start Lcn : 0x0000000000000000
Mft2 Start Lcn : 0x0000000000000000
Mft Zone Start : 0x0000000000000000
Mft Zone End : 0x0000000000000000
RM Identifier: 00000000-0000-0000-0000-000000000000

In the above result "Bytes per Cluster" represents the allocation unit size.

Best Allocation unit Size:

Higher the allocation unit size better the performance, but lower the disk space available, because data is written in units, if you write 1 byte the allocation unit consumed will be 4096, with 4098 bytes wasted.

Therefore if you are going to use a drive for large files like videos, or other multimedia formats, than higher allocation will be better. And for partitions that will hold documents like text files, etc. default allocation unit size is enough.

Size and Size on Disk:

If you are a windows user, you may have noted that when we view properties of any file or folder, the general tab mentions two sizes. One is the "Size" which is the actual size of the file and other is the "Size on disk" which is the space consumed on the drive.

The difference in both size indicate how much space has been wasted.