If you are installing OS/2 2.0 on a computer that does not contain an operating system, or if you choose to format an existing partition, you will be asked to choose a file system. You can select either HPFS or FAT.
The FAT file system has been enhanced under OS/2 2.0 to support caching, lazy writing, and the use of extended attributes. These features (described in Chapter 5, "Optimizing Performance") were available only with HPFS in previous versions of the OS/2 operating system.
The FAT file system is used by DOS. If users will be loading DOS from a diskette (while OS/2 2.0 is not running) and will need to have access to files in the OS/2 partition, format the OS/2 partition for FAT.
HPFS has features that make it a better choice for larger hard disks. It puts the directory at the seek center of the partition and is designed to allocate contiguous space for files. This feature helps prevent disk fragmentation. HPFS also handles write errors by writing to alternate space reserved for that purpose.
If you format an OS/2 partition for the FAT file system and the system memory is less than or equal to 6MB, support for HPFS is not automatically installed. You can add this support later (for example, if you want to format a partition for HPFS) using the Selective Install utility program (located in the System Setup folder).