Document 1201
SUPERSTOR - UTILITIES/TROUBLESHOOTING
JD/RS
2/6/92

                        UTILITIES

*Maintenance
Third Party - Most disk utilities, other than those shipped
with DR DOS 6.0, will not be able to properly define the
internal structure of a SuperStor drive. This is why it is
recommended that utilities which access internal drive
information SHOULD NOT be used on a SuperStor drive.    

DISKOPT - DISKOPT is a DR DOS 6.0 disk optimization utility
which is recommended for optimization of a SuperStor drive. 
DISKOPT is able to properly analyze the internal allocation
tables of a SuperStor drive by letting the SuperStor driver act
as an interpreter to the drive.

CHKDSK - CHKDSK is another DOS command which allows the analysis
of a drive. CHKDSK may be used to check the SuperStor drive
integrity and fix lost clusters which occurr on a SuperStor drive
or any on any other drive.  However, as noted below, CHKDSK may
not always accurately report available space on a SuperStor drive.

*Reported Statistics
Often the statistics reported by various DR DOS utilities and
third party utilities will vary with respect to space available
on a SuperStor drive.  This is due to the utilities' individual
understanding of SuperStor and its internal tables.

CHKDSK/Third Party Utilities - CHKDSK WILL NOT normally portray
the proper amount of available space on a SuperStor drive.  This
is because CHKDSK bases all of its information on a perfectly
formatted hard drive.  That is to say, CHKDSK will always assume
the optimum result. In SuperStor's case, CHKDSK will assume that
a perfect 2:1 compression ratio is always maintained.  However,
as SuperStor is used, its compression ratio will vary due to the
differing compression ratios of the individual files put on the
drive.  Some files will have better than 2:1 compression ratios
and some will have less than 2:1.  Therefore, actual statistics
will vary from CHKDSK and third party utilities as they are
using this perfect 2:1 compression ratio to calculate free
space.      

DIR/XDIR/SuperStor Statistics - DIR, XDIR, and the SuperStor
Statistics option may be used to properly determine the current
SuperStor free space.  All three of these options have
adjustments built into them to account for the different
compression ratios of each individual file kept on the SuperStor
drive.  In fact these three commands are kept aware of the
internal allocation tables which SuperStor keeps.

*Reserved Units
While performing a CHKDSK on a SuperStor partition, a user
may notice the reporting of: XXXX Bytes in SuperStor Reserved
Units.  Also, the user may notice a great reduction in the
amount of disk space free on their SuperStor partition.

SuperStor reserved units are entries in the SSTOR allocation
table that are marked as unusable due to the storage of
uncompressable data on the SuperStor partition.  Note: Table
entries refer to SuperStor's own internal allocation table;
uncompressable data is defined as that which cannot be
compressed further by using SuperStor (Arc'd, Zip, Gif files,
Exepacked files, etc.)  The following is an explanation of how
reserved units are applied:

                Actual Drive            SuperStored (compressed) Drive



                50 MB                   100 MB (2:1 compression ratio)

20% of drive    10 MB Zipped File                10 MB
(uncompressed)

                -----------------      ------------------------------

Space           40 MB Free Space                 90 MB Free
(reported)

SuperStor                                        10 MB
Reserved Units

                                               
                                       ------------------------------
                                                 80 MB                                                 80 MB Free
Space (actual)


Above: a 50 MB hard disk has been compressed with SuperStor to
create a 100 MB SuperStor partition.  On this partition exists a
uncompressable zip file 10 MB in size.  Prior to using SuperStor
the zipped file would have taken up approximatly 20% of the 50
MB drive. (i.e. 10MB zipped file / 50 MB of total space = .20 or
20%.)  The same applies after a SuperStor volume is created on
the drive.  However, in order to maintain the 20% occupancy of
the zipped file, 10 MB of Reserved Units are needed. i.e. 10MB
zipped file + 10 MB Reserved Units = 20 MB compressed.  20 MB
compressed / 100 total space (after SuperStor) = .20 or 20%.

Since the 10 MB zipped file cannot be compressed it is stored on
the SuperStor drive uncompressed.  It is actually using 10
physical MB of disk space (as if SuperStor had never been used).
 Since the zipped file was not compressed, it has essentially a
1:1 compression ratio (Remember, SSTOR cannot further compress a
file which already is compressed).  Using a CHKDSK /F may clear
the Reserved Units message shown previously by CHKDSK, but will
not free up the disk space.  In fact, the message will usually
reappear after a few reads or writes have been made to the
SuperStor partition.

Reserved Units will generally appear when your drive is 90% full
or greater.  If Reserved Units have appeared due to the storage
of uncompressable data on a SuperStor drive, move the
uncompressable data to a uncompressed drive. Then, free the
SuperStor Reserved Units by performing a CHKDSK /F on the
SuperStor drive.

*Backing Up a SuperStor Drive
Direct Memory Access- Todays backup software offer a vast array of
backup and restore options. Many of these backup options allow
Direct Memory Access (DMA) backups which are sometimes called
direct acess or fast backups. These types of backups do not use
conventional DOS routines. This method does not allow the SuperStor
driver (SSTORDRV.SYS) to act as a translator during the backup
process. Use of a DMA backup option on a SuperStor compressed
partition can result in a error message from the backup program
such as "Drive not ready".

Image Backup (or Mirror Backup)- Image backup options allow a user
to take an entire physical backup of a drive from begining to
ending cylinder of a drive. Think of it a as a photograph that
duplicates the entire contents of a disk including all system,
hidden and read-only files along with FATs and directories. These
backups are not recommended for a SuperStor drive as the
prospective restore drive may not properly accept the backup. The
restore drive MUST have the exact same parameters as the the backup
drive (drive size, total sectors, sectors per track, etc.).

File-by-File Backup- File-by-file backups are the most reliable
backup method for use on a SuperStor compressed partition. This
backup option will allow intervention of the SuperStor driver so
that files on the backup are uncompressed and can be restored to
either a compressed or a non-compressed drive.

                HELPFUL TROUBLESHOOTING TIPS


*If SuperStor will not compress a Non-bootable partition.

If SuperStor detects any files marked with the S for System
attribute, SuperStor will not install.  Use XDIR on the
prospective drive to locate files with the System attribute
active.  Then, remove these files, or their System attribute so
that SuperStor will execute.

*SuperStor has been used on a boot drive which was partitioned
with a 3rd party disk partitioning scheme.  Now, the drive
letters are out of sequence.

This is because the partitioning driver (Diskmanager, Speedstor)
is loading after the SuperStor (disk compression) drivers have
loaded.  Place the partitioning driver before the SuperStor
drivers in the correct configuration file.  Please see Tip #1200
for additional information regarding third party driver
placement with respect to a SuperStor drive.


*A third party disk partitioning scheme had been used on a drive
in which SuperStor has now been used to compress data.  All
precautions to move the partitioning driver to its correct
positioning have been taken.  However, several additional
"phantom" drive letter now appear which did not appear prior to
SuperStor.

Check to see if the disk partitioning scheme has a driver
loading in another configuration file as well.  Make sure that
this driver is only loading once in the appropriate location.
Please see Tip #1200 for further information regarding third
party driver placement with respect to a SuperStor drive.


*Available space on the SuperStor drive is quickly reduced

First, scan the current compression ratios of the various files
on the SuperStor drive.  Using the XDIR command will allow the
user to determine the compression ratios of each individual
file.  Once you have determined which files have poor
compression ratios (1.3:1 or less), you may wish to move them to
an uncompressed portion of the drive to improve the performance
of SuperStor.

Second, perform a CHKDSK on the SuperStor drive and see if there
are any bytes used by SuperStor Reserved Units.  If so, check
for and remove any files which may be uncompressable (those
which have a approximately a 1:1 compression ratio).  The
SuperStor Reserved Units may be freed up by performing a CHKDSK
/F.  However, the Reserved Units message in CHKDSK may reappear
if uncompressable data remains on the SuperStor drive.

        

Sources:	DR DOS 6.0 Optimization and Configuration Tips Guide 
		DR DOS 6.0 User Guide 	
