Category : HD Utilities
Archive   : STACTECH.ZIP
Filename : 2602.TXT

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STACKER NOTE STACKER NOTE
Title: Stacker Drive Space Reporting
STAC FAX Index #2602 - 2/10/93
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Background.

Use Stacker 2.0's SCHECK or Stacker 3.0's CHECK /D utility to see exactly
how the space has been used in the Stacker drive.

Here is an example of an SCHECK & CHECK /D report:

Volume in drive C is STACVOL_DSK
No errors found
Stacker Drive Statistics:

Stacker Drive STACVOL File
Drive C: D:\STACVOL.DSK
------------------- --------------------
Total Bytes: 4,109,312 2,054,656
Bytes Used: 3,735,552 ( 91.2%) 1,846,272 ( 89.9%)
Bytes Free: 373,760 ( 8.8%) 208,384 ( 10.1%)

Stacker Drive Compression Ratio = 2.0:1
Projected Bytes Free = 373,760


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 4 MB of data. There are enough clusters
left to acomodate 373,760 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:. It's name and
location are shown in the column title. In our example, D:\STACVOL.DSK is
2 MB in size and has used all but 208,384 bytes of that 2 MB. Therefore,
there are 208,384 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 2.0:1 ratio tells
us that the files in this Stacker drive are taking up half the space they
would take up on a "Non-Stacked" drive. (A 2.0:1 ratio is typical for an
average mixture of files.) 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: 208,386 x 2.0 or 416,772 bytes. However, we only have 373,760
bytes worth of unallocated clusters. Since the projected bytes free is
the smaller of these two numbers, it is 373,760. Fortunately, you can
increase the number of allocation units by "growing" the drive. To grow
the Stacker drive, run the Grow & Shrink utility from the STAC command
assistant. "Growing" the drive in this example would increase the
projected free space to 416,772.

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 1993, Stac Electronics