File Structure - ExFat

Here is a summary of the key points about the exFAT (Extensible File Allocation Table) file system

exFAT was developed by Microsoft in 2006 as a successor to the older FAT32 file system.

The main goals were to remove the 4GB single file size limit of FAT32 and increase maximum partition sizes.

exFAT supports extremely large file sizes up to 16 exabytes (16 million TB) and partition sizes up to 128 petabytes. This makes it ideal for large media files like 4K video.

It uses an allocation bitmap structure to track used and free space more efficiently than FAT32. Other optimisations include metadata checksums and flash storage optimisations.

exFAT is proprietary but Microsoft has released patents and specifications to allow free usage. It requires licensing for commercial use.

Compatibility has expanded over time - exFAT is supported natively in Windows, macOS, Linux (kernel 5.4+), and many consumer devices like cameras.

Key advantages of exFAT include no limits on file/partition sizes, efficient for large files and flash storage, and wide compatibility. Downsides are lack of advanced features like journaling.

On Linux systems without built-in exFAT support, installing the exfat-fuse package allows reading/writing exFAT drives.

In summary, exFAT overcomes the file size limitations of FAT32 while maintaining a relatively simple design, making it well-suited for modern large storage needs on removable media and devices.

Directory Structure

• ExFAT uses a flat directory structure without the hierarchical sub-directories found in FAT32.

• Each directory can hold up to 2,796,202 files, significantly more than the 65,534 file limit in FAT32.

File Name Lookup

• ExFAT employs a filename hash-based lookup mechanism to speed up file access, where a hash value of the filename is stored in the directory record.

Interaction with ExFat

Windows

• For Windows, you can use the Win32 API and the associated file system functions like CreateFile, ReadFile, WriteFile, etc.

• Programming languages like C, C++, C#, and Visual Basic can be used to develop applications that interact with the file system.

Linux

• On Linux, you can use system calls like open(), read(), write(), and the associated file I/O functions from the C standard library.

• Programming languages like C, C++, Python, and others can be used to develop applications that interact with the file system.

macOS

• On macOS, you can use the POSIX-compliant file system APIs like open(), read(), write(), and the associated functions from the C standard library.

• Programming languages like C, C++, Python, and others can be used to develop applications that interact with the file system.

Regardless of the platform, you would typically need to use low-level system calls or file system APIs to interact with the exFAT file system directly.

Alternatively, you can use higher-level libraries or frameworks that abstract away the low-level details and provide a more convenient interface for working with file systems, including exFAT.