Hard drive partitions and file system essentials

What most normal users need to know about hard disk partitions and filesystems to be able to move hard disks between various operating systems like Mac or Windows.


Hard disks contain 1 or more partitions. To the user, each partition appears as if it were a separate hard disk.

(In Windows, each partition receives a separate drive letter like C:, D:, etc.; on a Mac and most Linux, you see a separate icon on the desktop for each partition, and the contents is accessible in a folder like /Volumes/YourDiskName.)

The disk contains a partition table which describes the size and placement of the partitions on the disk. There are 2 main types of partition tables:


Every partition needs to be formatted with a file system to let the operating system store and retrieve files (on Mac, this formatting process is called "erasing"). There are many different types of file systems. Your system needs to understand these file systems to be able to use them. Unfortunately, various operating systems use different file systems. The problem is to find which one will be understood by all the systems you intend to connect your drive to. Also, some systems can only read certain file systems but cannot write to them (for example, Mac OS X can read but not write NTFS).

FAT or FAT32 or "MS-DOS"

This is the oldest of the file systems commonly used today. As such, it has the greatest compatibility and the least functionality. It is a sort of lowest common denominator. All operating systems can read and write to it. It is the file system generally used on USB flash drives, memory cards for photo cameras, etc. It cannot store files greater than 4 Gigabytes. It is also the least reliable of the current file systems, and has many other drawbacks (fragmentation, no support for permission, time stamps in local time, etc.)

The Windows disk manager refuses to format a FAT32 partition greater than 32 GB. But it can be formatted to the wanted size on Mac or Linux, or with the free fat32format utility in Windows.


Is the native file system of Windows. Macs can natively read NTFS, but can only write to it with additional programs 1. Recent Linux versions can both read it and write to it.

HFS+ or "Mac OS X Extended (journaled)"

Is the native file system on Macs.The Mac default is the HFS+ journaled variant. Windows needs special programs installed to be able to read or write it 2. Linux can read it when it has the hfsutils package installed. It can also write to it if journaling has been disabled 3.


Meant to replace FAT32 on digital cameras etc. While not as feature-rich and reliable as the others, it supports files greater than 4GB. So it's the simplest choice to exchange big files between Windows and Mac, when you don't know if the other machine has any special drivers installed.

Ext2 or Ext3

Is the official standard for DCP disks and the most common file system on Linux. You could try some Windows or Mac driver, but it's probably much easier to install Linux on some old machine and access it through the network.


And what about UDF, the "Universal Disk Format" which is even a true ISO standard? It is used on professional camera cards and on Blu-ray disks, and can in theory be read and written by all 3 current systems. But in practice, this is only true if it is correctly formatted. And since the normal formatting tools in Mac and Windows don't offer it as an option, I would only recommend it to geeks willing to use this command-line formatting script.


Below is a table trying to summarize the compatibility between the 3 main operating systems and the 5 main file system types. There are many others, but if you know about them, you probably don't need this page.

Windows Mac OS X Linux
FAT32 or DOS Native support
Max. 4GB. file size!
Max. 4GB. file size!
Max. 4GB. file size!
NTFS Native support Read only. Write support through additional software 1 Read/Write on recent distributions.
HFS+ or "Mac OS extended" Requires third party programs for reading and writing. 2 Native support Read only. Write if forced or journaling feature disabled. 3
Exfat Native support since Windows Vista/7 Native support since 10.6.5 Needs driver install 4
Ext2 or Ext3 Requires driver 5 Requires driver. 5 Native support

1. Mac -> NTFS: To enable writing of NTFS on a Mac, you need a commercial program like Paragon or Tuxera.
2. Windows -> HFS: If you only need to copy files from a Mac disk to your Windows machine, you can use the free HFSExplorer, which will open your drive in a Windows Explorer-like window and let you copy files from there. For full support, you may need commercial software like MacDrive or Paragon.
3. Linux -> HFS: If you need to write to the HFS disk, journaling must be disabled on a Mac first (through Disk Utility or diskutil disableJournal "/Volumes/YOUR_VOLUME_NAME"in Terminal). Alternatively, you can force the mount point to be writable.
4. Linux -> ExFAT: On Debian-based distributions like Ubuntu: sudo apt install exfat-fuse
5. Windows/Mac -> ext2/3/4: There are various free drivers for Windows and Mac, but when I tried them a few years ago, they were problematic. There is also a commercial driver from Paragon which I haven't tried. But really, a Linux machine on the network is so much easier.