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STACKER NOTE                           Stac Electronics Technical Note

Subject: Scheck and Stacker space reporting

Tech011 - 2/20/92
Page 1 OF 1
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Stacker's SCHECK utility offers information on the physical and logical
Stacker drive regarding total, used, and remaining bytes; percentage of
space used and free; compression ratio and projected bytes free.  Below
is a typical SCHECK report:

SCHECK - 2.0, (c) Copyright 1990-92 Stac Electronics, Carlsbad, CA
Volume in drive E is STACVOL_DSK
No errors found
Stacker Drive Statistics:

                  Stacker Drive             STACVOL File
                  Drive E:                  E:\STACVOL.DSK
            ----------------------          ----------------------
  Total Bytes:  4,096,000                   2,054,656
  Bytes Used:   3,735,552 ( 91.2%)          1,846,272 ( 89.9%)
  Bytes Free:     360,448 (  8.8%)            208,384 ( 10.1%)

Stacker Drive Compression Ratio = 2.0:1
Projected Bytes Free            = 360,448


What does it all mean?

The left hand column displays logical data on the Stacker drive.  This
is how DOS and CHKDSK see the drive.  The right hand column shows the
usage of space (physical) inside the STACVOL file.  This is the file
that contains all of your compressed data.  Its name and location are
shown in the column title.

Compression ratio:
The Stacker drive compression ratio is the average compression ratio
of the files in that specific STACKER drive.  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 non "Stacked" drive.  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
drive.  If the drive is less than 12% full, or if the drive compression
ratio is 2.0:1 or greater, this number will be the same as bytes free
in the Stacker drive (left column).  The projected bytes free on drives
with usage over 12%, or compression ratios less than 2.0:1, will be a
number slightly less than the bytes free in the STACVOL file multiplied
by the overall compression ratio.