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