Exfat mac allocation unit size. Sep 15, 2021 · I am currently using a PC (Win 7-10) - and I'm planning to get a Mac. The take away is that if you want a exfat external drive that works with both Mac and PC, make sure you format it on the Mac or set the unit allocation size to between 128K and 1024K. However, a couple of other writers claim 64Kb or even less should work. Is it also recommended to change the sectors-per-cluster (-c flag)? While HFS default is 4096 bytes, do we face any issues with using the same on exFAT? Dec 1, 2023 · Although the default allocation unit size for exFAT, if you format your SSD on Mac, will be 0. 5 kB. Oh yeah, thanks for clarifying about the device block vs allocation size. Since the smallest device block size is 512 bytes, the allocation block size can't be smaller. Sep 15, 2021 · In my online 'research,' a couple of writers claim that 128Kb is the lowest which will allow a MacOS to read/write the HD. This article introduces a professional disk management tool to help with changing the cluster size. Jan 13, 2026 · Looking for the best exFAT allocation unit size for PC or Mac? Here's how to choose the optimal allocation unit size for exFAT and how to check and change it. We would like to show you a description here but the site won’t allow us. 3 bytes. Is it also recommended to change the sectors-per-cluster (-c flag)? While HFS default is 4096 bytes, do we face any issues with using the same on exFAT? I solved this by formatting it on the Mac, which uses a 64K block size for exfat, which is still really large but 8x smaller than Windows. . For those handling a mix of file sizes, an allocation unit size between 8 KB and 16 KB offers the best balance. Mar 5, 2025 · To ensure compatibility between Mac and PC, format the exFAT external drive on a Mac or set the allocation unit size between 128K and 1024K. Aug 17, 2021 · exFAT supports greater file size and partition size limits than FAT 32. Nov 10, 2020 · Thanks, @DavidAnderson for the detailed answer. Nov 2, 2015 · 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. For a Apr 27, 2012 · I can reformat a brand new 2TB WD Passport drive to exFAT, with choice of many "Allocation Unit Size": 128kb 256kb 512kb 1024kb 4096kb 16384kb 32768kb which one is best if this drive is mainly use Dec 1, 2023 · Although the default allocation unit size for exFAT, if you format your SSD on Mac, will be 0. FAT 32 has a 4GB maximum file size and 8TB maximum partition size, whereas you can store files that are larger than 4GB each on a flash drive or SD card formatted with exFAT. exFAT’s maximum file size limit is 16EiB (Exbibyte). I know windows has very different default values on allocation unit size. Jul 4, 2025 · This page elaborates on the best exFAT allocation unit size and provides two ways to change and set exFAT allocation unit size. Examples: for a 100 GB partition the minimal size is 100,000,000,000 bytes/4,294,967,296=~23. Mar 16, 2023 · Do you know what the best allocation unit size for exFAT is? How to change the allocation unit size for exFAT partition? You can find answers in this post. To get the minimal size of an allocation cluster on your partition divide the size of your partition by 2^32. Nov 2, 2015 · The maximum allocation block (or cluster) count for exFAT is 2^32 = 4,294,967,296. Thing is, when you copy files from a Mac to a windows-format file system, about a third or maybe half the files end up with a shadow metadata file, which on the Mac are 4K each. 1) I plan to use the PC's Command Prompt for the formatting - thus, what is the smallest allocation unit size which I can use when setting up external hard drive (HD) with an exFat format ? 2) Is a full format necesary to change the allocation unit size? Or, is a quick format May 18, 2019 · I've come to believe that it is the default file allocation unit size that Windows assigns to exFAT formatted drives that can often be the culprit, but I can find no information about what the file allocation unit should be used for compatibility with macOS? Any help is appreciated! Thanks. zqrrz ngmtt bvrp zqyvbh hovkwvk puzcc dmf cftzq bpoo jtgcze