FAT contains the following enhancements that provide improved
performance and enhanced support for disk hardware devices:
- Command chaining by attempting to call the volume manager with a
list of all contiguous sector requests required to fill an I/O
request. This enables multiple page-in and page-out requests in a
single logical operation.
- Scatter and gather by passing physical pointers to each page in
the data buffer (physically not contiguous) as part of the I/O
request. This enables I/O controllers that support the
scatter-and-gather capability, such as the IBM SCSI adapters, to
perform input/output in a single operation.
- Disk caching is now within the FAT file system, rather than in the
device driver
- Recognition of devices that have outboard caches (nonsystem
memory), incorporating them into the total caching scheme
- Fast allocation of free space, using a bit map to track free
clusters on the disk