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      STACKER NOTE                                         STACKER NOTE
                    COMPRESSING LARGE DRIVES WITH STACKER
                 (Applies to Stacker 3.x for Windows & Dos)
      STAC FAX  3507 (01-11-1994)
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      BACKGROUND
      
      Stacker uses cluster size to determine the largest compressed
      partition that it can make. This is important if you plan to
      compress a physical partition larger than 256 MB.  During Setup
      Stacker will default to an 8 KB cluster size.  This means that a
      default installation on a partition larger than 256 MB may result
      in multiple compressed drives. If you desire a single compressed
      partition instead of the default configuration, you may need to
      choose a larger cluster size.  Because cluster size is determined
      during Setup it cannot be changed after the Stacker partition has
      been created.
      
      SOLUTION
      
          Determine the expected size of the compressed partition.
          Choose the correct cluster size for the compressed
           partition.
          Be aware of issues concerning large partitions.
           
      DETERMINE THE SIZE OF THE COMPRESSED PARTITION
      
      The size of the compressed partition will be determined by the
      physical size of the partition and the compression ratio.  The
      default compression ratio is 2 to 1. Unless you are an
      experienced Stacker user, accept the default compression ratio.
      
      Multiply the physical size of the partition by the expected
      compression ratio. For example, a 240 MB partition at the default
      2 to 1 compression ratio results in a 480 MB compressed partiton.
      The same physical partition at a 3 to 1 compression ratio results
      in a 720 MB compressed partition. The result of the calculation
      is the expected compressed partition.
      
      CHOOSE THE CORRECT CLUSTER SIZE
      
      Note: If you find the default configuration satisfactory, Stacker
      Setup will choose the best cluster size for you.
      
       1. If your drive is already compressed, uncompress all the
           partitions. See your Stacker User's Guide for details on how
           to run the UNSTACK command.
       2. Run the Stacker Setup. Choose Custom Setup, Advanced
           Options.
       3. At the Advanced Options screen, tab to the Cluster Size
           selections. Choose the correct cluster size for the expected
           compressed partition that you calculated.
           If the expected compressed partition is less than 512 MB,
      choose "auto".
      
           If the expected compressed partition is 512 MB to 1 GB,
      choose 16K clusters.
      
           If the expected compressed partition is 1 GB to 2 GB, choose
      32K clusters.
      
         4.Continue compressing the drive in accordance with the
           instructions on your screen.
           
      ISSUES CONCERNING LARGE PARTITIONS
      
       1. When using clusters that are larger then 8 KB, the memory-
           resident portion of the Stacker device driver will increase
           significantly.  To offset this increase, you may load the
           cache portion of the driver into the upper memory blocks or
           expanded memory (if available). You may use the /EMS switch
           if you have expanded memory available. And if you have
           sufficient upper memory blocks you may use the /UM switch.
           For Stacker version 3.0, refer to pages 218-221 of your
           Stacker User's Guide. For Stacker 3.1, refer to Stacfax
           31014.
       2.  Another result of using large partitions is that drive
           access may be slower due to the increased size of the
           directory and file structures.  Your system may not have
           enough memory to allow your disk repair utility to process
           the directory structure of your large drive.  Also, some
           disk repair utilities may not be compatible with 32 KB
           clusters (check with the manufacturer of your utilities).
       3.  Stacker Coprocessor cards do not support the use of
           clusters larger than 8 KB.
           
      
      
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      Copyright 1994 Stac Electronics