In computer file systems, a cluster or allocation unit refers to the smallest logical amount of disk space allocated to hold a file. Well, the size of a single cluster is decided by the Allocation Unit Size selected when the partition is created or formatted. The other name of allocation size is Cluster Size. In case your drive has a lot of small size files, it is better to set the allocation size small, as it will save the space on your computer.
If it is not set correctly, it may reduce the data read-write speed and waste a lot of disk space. The speed of the hard drive depends on the size of clusters. If you have tons of smaller files, a larger allocation size will eat up your drive space slightly faster. Here, in this article, we are providing the best and perfect allocation size.
What Allocation Size is Perfect?
The optimal allocation unit size for your drive will often depend on which operating system you’re using and how the size of the disk is—using larger than necessary allocation unit sizes- can create unnecessary fragmentation on your drive. So it is essential to change cluster size reasonably.
In most cases, Microsoft recommends an allocation unit size of 4 KB, and 64k cluster size is widely used among users who store big files like games, 3D movies, HD photos, etc. It is what the company says works best for “standard users.” If you need a non-default size, you probably already know that and why you need it.
The recommended cluster size for a 64GB FAT32 partition is 16KB, the recommended cluster size for a 128GB FAT32 partition is 32KB, and the recommended cluster size for a 256GB partition is 64KB. One cluster can only hold one file, but one file may take up multiple clusters depending on the file size and the cluster size.
Cluster Size For exFAT:
If the file’s actual size is more than a cluster, it will take up two or more clusters. If you have no idea about your file size and unit, Default is also a good choice. It will choose a proper cluster size for your drive based on the capacity. For example, according to Microsoft, the executing standard of default cluster size for exFAT is:
- 7MB – 256MB: 4KB
- 256MB – 32GB: 32KB
- 32GB – 256TB: 128KB
- >256TB: Not supported
Cluster Size For ReFS:
ReFS offer both 4K and 64K clusters. 4K is the default cluster size for ReFS, and we recommend using 4K cluster sizes for most ReFS deployments because it helps reduce costly IO amplification. By choosing 4K clusters instead of 64K clusters, one can reduce the number of IOs that occur smaller than the cluster size, preventing costly IO amplifications from occurring as frequently.
NTFS Cluster Sizes:
NTFS offers cluster sizes from 512 to 64K, but in general, we recommend a 4K cluster size on NTFS, as 4K clusters help minimize wasted space when storing small files. There are two cases, however, where 64K clusters could be appropriate:
- 4K clusters limit the maximum volume and file size to be 16TB
- 64K cluster sizes can offer increased volume and file capacity, which is relevant if you’re are hosting a massive deployment on your NTFS volumes, such as hosting VHDs or a SQL deployment.
How to Change File Allocation or Cluster Unit Size?
Through Command Prompt:
- Press Windows + R to open Run.
- Type cmd and press Ctrl + Shift + Enter to run Command Prompt as administrator.
- Input disk part and press Enter to open diskpart.exe.
- Input the following commands and press Enter after each: List disk, Select disk * (* refers to the number of the target disk or partition), List partition, Select partition *, Format fs=ntfs unit=64k.
Through File Explorer:
- Double-click This PC to open File Explorer.
- Right-click the partition for which you want to change cluster size, and then choose Format.
- You can see the current Capacity, File system, and Allocation unit size of the partition in the pop-up window. Now, open the drop-down menu of Allocation unit size to choose your desired value, check Quick Format, and click Start to format the partition.
Through Third-party Utility:
- For the sake of security, we recommend using a reliable third-party utility. You can use its Pro Ultimate version to achieve this within a few clicks without formatting. They also provide the instructions guide to change the cluster size.
Final Words:
If you’ve ever formatted a hard drive or USB thumb drive, you might have seen the “Allocation Unit Size” setting. It is also known as cluster size, which determines the smallest chunk of disk space that holds a file. If the cluster size is large, the space on the disk will be wasted. After reading this article, you will get to know which allocation or cluster size is best for exFAT, NTFS, and ReFS.