High Performance File System Changes

The following changes have been made to the High Performance File System (HPFS) driver under OS/2 Version 2.0:

  • At initialization time, the level of support provided by the device driver is determined using the new device command 1DH - GetDeviceSupport.

  • The HPFS driver passes physical addresses for data pointers, in the appropriate request format, to the device driver.

  • The HPFS driver now supports command chaining, calling the volume manager with a list of all contiguous sector requests required to fulfill an I/O request.

    This function is supported for all DASD types.

  • The HPFS driver supports scatter/gather by passing physical pointers to each page in the data buffer (physically discontiguous) as part of the I/O request.

    This allows I/O controllers such as the IBM SCSI adapters which support the scatter/gather capability to perform the I/O in a single operation.

  • The HPFS driver now supports disk caching in the IFS driver, rather than in the device driver.

  • The HPFS driver is able to recognize devices which have outboard caches (non-system memory), and incorporate them into the total caching scheme.

    The HPFS file system under OS/2 Version 2.0 supports a maximum file size of 2GB. The maximum size for an HPFS volume is 512GB.

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