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2.9 Compound File Size Limits

The minimum size of a compound file is one header, one FAT sector, and one directory sector, which is 3 sectors total. Therefore, a compound file MUST be at least 3 sectors in length.

A 512-byte sector compound file MUST be no greater than 2 GB in size for compatibility reasons. This means that every stream, including the directory entry array and mini stream, inside a 512-byte sector compound file MUST be less than 2 GB in size.

4096-byte sector compound files can have 64-bit file and user-defined datastream sizes, up to slightly less than 16 terabytes (4096 bytes/sector x MAXREGSECT (0xFFFFFFFA) sectors).

The maximum number of directory entries (storage objects and stream objects) is MAXREGSID (0xFFFFFFFA), roughly 4 billion. This corresponds to a maximum directory sector chain length of slightly less than 512 GB for a 4096-byte sector compound file.

The maximum number of directory entries (storage objects, stream objects, and unallocated objects) in a 512-byte sector compound file is limited by the 2 GB file size, resulting in 0x00FFFFFF (slightly less than 16 million) directory entries.

The maximum size of the mini stream is MAXREGSECT (0xFFFFFFFA) x 64 bytes, which is slightly less than 256 GB. The maximum size of the mini stream in a 512-byte sector compound file is limited by the 2 GB file size.

 
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