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      STACKER NOTE                                         STACKER NOTE
                    COMPRESSING LARGE DRIVES WITH STACKER
                 (Applies to Stacker 4.0 for Windows & DOS)
      STAC FAX  4505 (02-22-1994)
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      BACKGROUND
      
      Stacker uses cluster size to determine the largest compressed
      partition that it can make. During Setup Stacker will examine
      your drive for the size of its partitions. Setup will then select
      the cluster size that will compress each partition with the
      fewest possible divisions.  Because cluster size is determined
      during Setup it cannot be changed after the Stacker partition has
      been created.
      
      SOLUTION
      
          - Determine the size of your expected compressed partition.
          - How Stacker selects cluster size.
          - Be aware of issues concerning large partitions.
          - Change your cluster size if desired.
           
      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.
      Multiply the physical size of the partition by the expected
      compression ratio. For example, a 180 MB partition at the default
      2.5 to 1 compression ratio results in a  450 MB compressed
      partition. The same physical partition at a 3 to 1 compression
      ratio results in a 540 MB compressed partition. The result of the
      calculation is the expected compressed partition. Unless you are
      an experienced Stacker user, accept the default compression
      ratio.
      
      How Stacker Setup selects cluster size.
      
      Stacker Setup will select cluster size based on the size of the
      expected compressed partition.
      
          If the expected compressed partition is less than 512 MB,
           Setup will choose 8K clusters.
          If the expected compressed partition is 512 MB to 1 GB,
           Setup will choose 16K clusters.
          If the expected compressed partition is 1 GB to 2 GB, Setup
           will choose 32K clusters.
           
      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). And if you have sufficient
           upper memory blocks you may use the /UM switch. Stacfax 4004
           provides information on how these switches are used in the
           STACKER.INI file.
       2.  If you are using a '386 computer or later, have more than
           1MB of RAM, and DOS 6 or later, you may use the DOS
           Protected Mode Services (DPMS).  This will automatically be
           configured for you during Setup.
       3.  QEMM's Stealth Mode: If DPMS is not available and if your
           drive will be using 32K clusters, Stacker's Setup will
           default to "Use EMS" (Expanded Memory Services). It does
           this to offset the increase in driver size mentioned in
           paragraph 1. However, QEMM's Stealth Mode cannot access
           memory using EMS. In thes case, insert the option /DBF=2 on
           the QEMM386 line of your CONFIG.SYS file.
       4.  You need at least 585K free conventional memory to run the
           Stacker Setup (Create) on a large drive that uses 32K
           clusters. Each system will vary. For example, we have noted
           a requirement on one system of 620K free when compressing a
           large magneto-optical drive.
       5.  Drive access on large partitions 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 or defragmenter to process the directory structure
           of your large drive.  Also, some disk repair utilities and
           defragmenters may not be compatible with 32 KB clusters
           (check with the manufacturer of your utilities).
       6.  If you are using 32K clusters the Stacker Optimizer,
           SDEFRAG.EXE, may have insufficient memory to run. If so, you
           may need to run SDEFRAG with a special option. This option
           affects speed, but allows it to run in less memory. From the
           DOS prompt, type:
            SDEFRAG /buffer=#
           where # is a value between 256 and 4096, inclusive. The
           following examples show how much memory is saved with
           various values:
            SDEFRAG /buffer=3072       21K memory saved
            SDEFRAG /buffer=2048       42K memory saved
            SDEFRAG /buffer=256        78.75K memory saved
           By default, SDEFRAG normally runs at /buffer=4096.
           
      Change your cluster size if desired.
      
      If you decide that you wish to use cluster sizes other than the
      default, you must uncompress your drive and run Setup again.
      
       1.  If your drive is already compressed, uncompress the
           partitions that you wish to change. See your Stacker User's
           Guide for details on how to run the UNCOMP 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 desired cluster size.
        4. Continue compressing the drive in accordance with the
           instructions on your screen.
           
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      Copyright 1994 Stac Electronics
