In brief, use 'fx' to format and label (partition) the drive, use
  'mkfs' to create the empty filesystem, create the mount points and put
  the proper entries into /etc/fstab.  The IRIX Site Administrator's
  Guide describes this in detail.

  Most disks come already formatted.  Don't format a disk which is
  already formatted; it wastes time and may cause problems. Some disks
  come with an SGI filesystem already installed, so you may not even
  need to label the disk or 'mkfs'.

  Dave Olson of SGI <olson@sgi.com> adds: "The 5.3 disk tool (for scsi
  disks only) can create the header for you also, as well as set up the
  partitions as on option disk (and only that).  Unfortunately, the
  initialize button does a -c FORMAT, not -c INITIALIZE to fx, so it
  takes longer than it should, and violates my oft-stated "don't ever
  format a scsi disk unless you absolutely have to do so" dictum.  It's
  fixed for 6.1 and beyond.

  Quantum's Grand Prix drives need extra fiddling; see
  http://www.quantum.com/support/faq/faq.htm#scsi9.