The allocation unit size is the smallest unit that the system reads and writes to disks and Removable storage devices. The file is stored on disk according to the size of the allocation unit. In general, the smaller the allocation unit, the more space, in the process of reading need a long time, and the larger the allocation unit waste space, in the process of reading need a relatively short time;
For example: For a 500-byte file, when you set the allocation unit to 512 bytes, it occupies only 512 bytes of storage; When you set the allocation unit to 1024 bytes, it occupies 1024 bytes of storage space; When you set the allocation unit to 4096 bytes, It occupies 4096 bytes of storage space, so the smaller the allocation unit, the more space, in the process of reading will take a long time. But when we set the allocation unit to an hour, it's equivalent to dividing a file into chunks that are stored in the U disk, which can result in slower reads.
When you format the U disk, the system automatically resizes the allocation unit for the file system format.
Format is FAT32
Format is NTFS
Format is exFAT
Allocation unit size, the first is to the U disk format, under normal circumstances, the system will automatically allocate a good allocation unit size, you can not change, but if there is a special need, you can manually set the size of the allocation unit you need.