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      STACKER NOTE                                         STACKER NOTE
                         STACKER 4.0 SPACE REPORTING
                          (Applies to Stacker 4.0)
      STAC FAX  4603 (05-02-1994)
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      BACKGROUND.
      
      Use Stacker's CHECK /D utility to see exactly how the space has
      been used in the Stacker drive. Type: CHECK /D drive: <enter> for
      a report on the desired Stacker drive. Here is an example of a
      CHECK /D report:
      
         Volume in drive C is STACVOL_DSK
         No errors found
         Saving header information... C:
         Stacker Drive Statistics:
      
                                                              
      STACVOL File                                 Stacker Drive
      D:\STACVOL.001                               Drive C:
      -----------------------                     -------------------
      Total Bytes:                                  33,447,936
      16,078,848
      Bytes Used:                                   28,844,032 ( 86.2%)
      13,862,912 ( 86.2%)
      Bytes Free:                                   4,603,904 ( 13.8%)
      2,215,936 ( 13.8%)
      
      Bytes per Cluster:  8,192                      4,096
      
      Stacker Drive Compression Ratio           = 2.1:1
      Projected Bytes Free                      = 4,603,904
      Fragmentation Level                       = 0%
      
      What does it all mean?
      
      The Left Hand Column:  This column displays "logical" data in the
      clusters on the Stacker drive.  In this example, it tells us that
      there are enough allocation units (clusters) for 33.4 MB of data.
      There are enough clusters left to accommodate 4,603,904 bytes of
      data.  The DOS CHKDSK program reports these numbers because it
      looks at allocation units.
      
      The Right Hand Column:  This column shows the usage of actual
      physical hard disk space inside the STACVOL.DSK file.  The
      Stacvol file contains all of the data and free space for the
      Stacker drive C.  Its name and location are shown in the column
      title.  In our example, D:\STACVOL.DSK is 16 MB in size and has
      used all but 2,215,936 bytes of that 16 MB.  Therefore, there are
      2,215,936 bytes of physical free space left in D:\STACVOL.DSK.
      
      Compression ratio.
      
      The Stacker drive compression ratio indicates the average
      compression of the files in that drive.  The compressibility of
      the files is generally dependent on their contents.  In the above
      example, the 2.1:1 ratio tells us that the files in this Stacker
      drive are taking up somewhat less than half the space they would
      take up on an uncompressed drive. (A 2.1:1 ratio is lower than
      the Stacker 4.0 default of 2.5:1. It indicates that some of the
      files on the drive do not compress well.)  A drive full of
      graphics files may achieve an average compression of 8.0:1 or
      more.  An 8.0:1 ratio would mean that the files are taking up 1/8
      the space they would on a standard drive. Conversely, some files
      are already compressed, such as "zipped" files. Stacker will not
      attempt to compress previously compressed files, so they will
      bring down the overall compression ratio of the Stacked drive in
      which they reside.
      
      NOTE: The drive compression ratio does not display if the drive
      is empty.
      
      Projected bytes free.
      
      This number is Stacker's estimate of the available space left on
      the Stacked drive.  It is determined by multiplying the physical
      free space (right side) by the compression ratio, OR by the
      number of clusters left unallocated (left side).  The projected
      bytes free is limited to the smaller of these two values.
      
      In our example, physical space free multiplied by the compression
      ratio would be: 2,215,936 x 2.1 or 4,653,465 bytes. However, we
      only have 4,603,904 bytes worth of unallocated clusters.  Since
      the projected bytes free is the smaller of these two numbers, it
      is 4,603,904.
      
      Notes:  When the number for physical bytes free goes to zero, the
      drive is full.  You cannot "grow" the drive to create more
      physical space.  Also, if the drive is less than 12% full, the
      projected bytes free will equal the "logical" bytes free number
      (left column).
      
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      Copyright 1994 Stac Electronics