To format a partition use newfs_exfat /dev/disk*s* The minimal possible allocation block size is then 1024 bytes.

Since the smallest device block size is 512 bytes, the allocation block size can't be smaller.įor a 3 TB partition the minimal size is 3,000,000,000,000 bytes/4,294,967,296=~698.5 bytes. To get the minimal size of an allocation cluster on your partition divide the size of your partition by 2^32.įor a 100 GB partition the minimal size is 100,000,000,000 bytes/4,294,967,296=~23.3 bytes. The maximum allocation block (or cluster) count for exFAT is 2^32 = 4,294,967,296. So looks like chkdisk showed same 131072 bytes per cluster Just booted back to Mac and run the command sudo newfs_exfat -N /dev/disk0s6: Reformatting existing ExFAT volume I didn't found a way how to check cluster size on Mac so I boot in Windows and run chkdsk on that drive:Īs you can see 131072 bytes in each allocation unit - that is my current cluster size being created by Mac DiskUtil default Here is an example of files in folder bower_components which is 46.1 MB taking 9.75 GBspace on the disk (printed from windows): I have lots of small files in that volume and my small files took to much physical space so I want to reformat the volume with a minimum Device Block Size and Cluster Size so my small files won't take any additional space.

I have an 512 GB SSD on my MacBook Retina with one of the volumes disks0s6 formatted with exFat to use it on both Mac and Windows.ĭiskutil info disk0s6: Device Identifier: disk0s6ĭevice / Media Name: Basic data partition

Diskutil format fat32