About block size and cluster size
According to Wikipedia, in computing, a block is the size of a block in data storage
and file system. Block, sometimes called a physical record, is a sequence of bytes
or bits, usually contain some whole number of records, having maximum length, a
block size. Block size, the minimal unit of data for block ciphers. In modern
cryptography, symmetric key ciphers are generally divided into stream
ciphers and block ciphers. Block ciphers operate on a fixed length string
of bits. The length of this bit string is the block size.
When operating system read and write files, it will read and write according to the
cluster size of file system. The file system is generally based on Cluster size,
sometimes called Block size to read and write data. This Cluster is generally the
smallest 4K, and the large size is 32K, 64K, which is depending on the application.
For example, the application of Oracle is generally used in 4K or 8K Block size, and
large file read-write can be used with 128K or even 256K.
Why change block size from 4K to 64K?
At the very first, the 512 bytes cluster is the standard. With the develop of
technology, the 4K is common now. And the 64K is for big file storage like game, 3D
movie, HD photo. You will benefit from the 64K cluster size. For example, games like
warcraft, overwatch, install package are big, the large cluster size like 64K will
significantly improve its performance.
How to change block size from 4KB to 64KB?
But how to change block/cluster size from 4KB to 64KB? Here we provides you the best
three ways to do it.
* If you do not want to lose any data on the partition, you should
copy partition for backup in advanced.
Change cluster size in Windows File Explorer
You can try to use Windows File Explorer to change block/cluster size by formatting
partition.
1. Press Win + E to open Windows Explorer. Right-click the
partition which you want to change the block/cluster size, select
Format... (Format partition will delete all data on the
partition, please make sure you have already backed up the data on partition).
2. In the format dialog, click Allocate unit size, select 64
kilobytes, and select Quick Format, and click on
Start.

3. Wait till the progress done.
Change cluster size from 4K to 64K with command prompt
You can also change block size from 4K to 64k with command prompt. Of you do not know
how to do it, follow the guides below:
1. Click Start, type cmd in the search
box, and then, run the command prompt as administrator.
2. Then, you can type the following command in order (each command will be
executed by pressing Enter).
diskpart
list disk
select disk n (n refers the disk number that the partition
which you want to change cluster size on)
list partition
select partition m (m refers the partition number that you want
to change cluster size)
format fs=ntfs quick unit=64k
exit

Format partition to change cluster size from 4K to 64K with AOMEI Partition
Assistant
Using a third party software to change block/cluster size from 4K to 64K should be
the easiest way. AOMEI Partition
Assistant is such an easy-to-use freeware that can help you format
partition to change cluster size from 4K to 64K without losing data.
Step 1. Free download AOMEI
Partition Assistant Standard, install and launch it. If you do not want to lose
data, you can use copy partition
wizard to copy the partition first.
Step 2. The, you can format partition with AOMEI Partition
Assistant to change cluster size from 4K to 64K. Right click the partition,
select Format Partition.

Step 3. In the format partition window, you can change cluster
size in the drop-down menu, here you can choose 64KB to change cluster size from 4KB
to 64KB. Click OK.

Step 4. Here you will back to the main interface, click
Applyat the toolbar and then click Proceed to
execute the whole operation.
Wait till the progress reaches 100%. Close the program to quit it.
Conclusion
Those three methods all can help you change block size from 4K to 64K. But we highly
recommend the software AOMEI Partition Assistant, the great partition manager, can
not only help you change cluster size from 4KB to 64KB, but also solve you many
other partition problems. For example, if you do not satisfied the partitions on
your hard drive, you can use it to repartition
hard drive with a few mouse clicks. Besides, you can upgrade to AOMEI Partition Assistant
Professional to get more advanced features, for example, if you use an
SSD, it supports you to do 4K partition
alignment which can optimize its performance.