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Text File | 1991-08-25 | 20.3 KB | 601 lines

DF Disk Free Space Utility Version 2.02 August 25, 1991 Copyright (c) 1991 R. E. Faith. All rights reserved. CompuServe: 72571,2241 InterNet: faith@cs.unc.edu DF Documentation August 25, 1991 OVERVIEW OF FEATURES o Displays disk free space information for all drives on system o Calculates percent-available space for each drive o Provides summary of disk space for whole system o Calculates disk storage "efficiency" o Identifies JOIN'd, SUBST'd, and Network drives o Identifies Stacker volumes o Displays SSWAP mappings o Calculates system totals not counting the physical STACVOL files o Provides internal data about Stacker volumes o Calculates special "efficiency" values for Stacker volumes o Provides all Stacker-specific data when run under DESQview INTRODUCTION DF is a UNIX-like Disk Free Space utility. For each drive on the system, it will display the drive letter, volume name, and the total number of kilobytes on the drive. The number of kilobytes used and available is also displayed, as well as a percentage value indicat- ing how much of the disk space is available. DF will identify Stacker volumes, Network'd, SUBST'd, and JOIN'd drives. When Stacker volumes are present, an estimate of total "usable" disk space is generated at the end of the DF output. The "usable" disk space does not include the disk space which is taken up by the physical STACVOL files, and only includes the space which is avail- able for actual use on the system. Command-line options are provided to obtain information on a specific drive, and to calculate statistics regarding how effe- ciently the drive is storing data. This "efficiency" rating com- pares the actual number of bytes in all of the files on the drive with the number of bytes used to store these files. Since the Version 2.02 - 1 - DF Documentation August 25, 1991 smallest allocation unit on a disk drive is the cluster, there is some overhead (about 1 kbyte per file when 2 kbyte clusters are used). Command-line options are also provided to obtain cluster size information, and to obtain Stacker-specific information. The Stacker software compresses data and stores these data in the STACVOL file using the sector (512 bytes) as the smallest unit of allocation. DF will report the number of free sectors in the STACVOL file. When the "efficiency" option (-e) is used with the Stacker-specific information option (-S), additional statistics will be provided. DEFAULT INFORMATION The default (i.e., with no command line options) invokation of DF will provide information in the following form: Drive total kb used free % avail C:Root 37538 30882 6656 18% D:Stac_User 20284 20256 28 0% H:User 40192 37576 2616 S 7% JOIN C:\USR Totals 98014 88714 9300 9% Usable 77758 68458 9300 12% The drive letter is displayed, followed by the volume label, if available. The "total kb" and "free" information is from the DOS "Get Disk Free Space" function (36h). The "used" information is obtained by subtracting the "free" value from the "total kb" value. The "used" value may be artificially high on Stacker volumes, since the Stacker software attempts to provide an accurate estimate of disk free space. The Stacker software will decrease the reported free space value when poor compression ratios are detected. The "S" following the "free" value for drive H: indicates that this drive is a Stacker volume. The last column shows that drive H: has been JOIN'd to C:\USR. SUBST'd and Network drives are also noted in this column. The "Totals" row is a straight summation of the previous information. When a Stacker volume is present, the "Usable" row will indicate similar totals not counting the space used by the physical STACVOL file. In this case, the STACVOL file for drive H: is on drive D: and takes up 20256 kbytes. The "Usable" row accurately Version 2.02 - 2 - DF Documentation August 25, 1991 represents the additional space provided by Stacker volumes, and more appropriately calculates the percentage of available space. COMMAND-LINE ARGUMENTS: FILENAMES A filename can be placed on the command line, and information about the drive that the file is on will be displayed. The most common filenames are drive letters (i.e., DF A:) and "." (i.e., DF .), which provides information about the current drive. This is espe- cially useful if you have forgotten the drive letter of the drive that you are using, or if that drive is JOIN'd. In the latter case, most directory programs will disregard the JOIN and report free space information for the host drive. COMMAND-LINE OPTIONS: -a Normally, DF does not scan the floppy drives. This can be time consuming, especially if the drives are empty. The "-a" switch forces all drives, including floppies to be scanned. To use DF on a single floppy, without getting information on all of the others, use "DF A:" COMMAND-LINE OPTIONS: -v The "-v" switch provides verbose information: Drive total kb used free % avail C:Root 37538 30882 6656 18% 4 sectors per cluster ( 2048 bytes) PHYS D:Stac_User 20284 20256 28 0% 4 sectors per cluster ( 2048 bytes) PHYS H:User 40192 37576 2616 S 7% JOIN C:\USR 20256 physical kbytes D:\STACVOL.000 16 sectors per cluster ( 8192 bytes) PHYS JOIN Totals 98014 88714 9300 9% Usable 77758 68458 9300 12% The additional information displayed includes the number of sectors per cluster and the cluster size. This can be helpful when setting up disk drives, since it is less wasteful to use the smallest cluster size available (2048 bytes under DOS). Stacker volumes, in general, use 8k clusters. This may make the Stacker compression algorithm more efficient. Version 2.02 - 3 - DF Documentation August 25, 1991 Flags from the Current Directory Structure are shown in the last column. The flags are PHYS (for physical), JOIN, SUBST, and NET. For Stacker volumes, the name and physical size of the STACVOL file is displayed. COMMAND-LINE OPTIONS: -S The "-S" switch provides Stacker-specific free space information: Stacker version 1.12 installed Drive total kb used free % avail C(C):Root 37538 30882 6656 18% D(D):Stac_User 20284 20256 28 0% H(H):User 40192 37576 2616 S 7% JOIN C:\USR 40192 33128 7064 18% <= FAT data 20102 18599 1503 7% <= STACVOL data Totals 98014 88714 9300 9% Usable 77758 68458 9300 12% The Stacker driver version number is displayed. (This is the driver loaded in CONFIG.SYS.) (The current version of DF will not work with Stacker versions other that are not currently available for testing. If you have one of these versions, and wish to explore uncharted waters, you can use the "-f" switch to force DF to ignore the Stacker version number. This may lead to the reporting of incorrect information and/or cause DF to crash. The "-f" switch should be considered an undocumented feature of DF. The use of the "-f" switch is NOT recommended. Please try to find an updated version of DF as soon as possible.) In the first column, after the drive letter, another letter is present which shows the drive letter for this drive at boot time. This should be the same as the information displayed by the Stacker program SWAPMAP. DF, however, can provide this information when run under DESQview. The row labeled "FAT data" is computed by walking the File Allocation Table and counting the clusters in use. These data should be identical to the default information for the drive, except when poor compression ratios have caused the Stacker software to provide a conservative estimate of disk free space (as in the ex- ample above). These data could also different if the drive has been corrupted and CHKDSK and/or SCHECK need to be run. Version 2.02 - 4 - DF Documentation August 25, 1991 The row labeled "STACVOL data" is computed by walking the sector allocation table in the STACVOL file. Although the Stacker volume is using 8k clusters as the smallest allocation unit, the STACVOL file uses 512 byte sectors as the smallest allocation unit. When compression ratios are poor, more sectors will be needed to store data. When the Stacker software runs out of either clusters (FAT entries) or sectors, the drive is full and no more files can be stored. Many short files will use up FAT entries faster, whereas compressed files will use more sector space. COMMAND-LINE OPTIONS: -e The "-e" option evaluates the "efficiency" of storage on the drive. The smallest allocation unit on a disk drive is the cluster. This means that if a file is only one byte long, it will take up a full cluster on the disk drive. For 2k clusters, it follows that, on average, approximately 1k of storage will be "lost" by each file. The "-e" option provides information about this loss: Drive total kb used free % avail C:Root 37538 30882 6656 18% 29532 kbytes in files Efficiency = 95% D:Stac_User 20284 20256 28 0% 20256 kbytes in files Efficiency = 100% H:User 40192 37576 2616 S 7% JOIN C:\USR 23688 kbytes in files Efficiency = 69% Totals 98014 88714 9300 9% Usable 77758 68458 9300 12% The value labeled "kbytes in files" is computed by adding together the number of bytes used by each file (NOT rounded to the nearest cluster). The "Efficiency" represents the ratio of this number to the number of kbytes used when each filesize IS rounded to the nearest cluster. For this calculation, the sizes of all directories are ignored. In general, the "Efficiency" computed is very close to the number found by dividing the "kbytes in files" by the "used" value (which includes the clusters used by directories). When the "-e" switch is used with the "-S" switch, additional Stacker-specific information is provided: Version 2.02 - 5 - DF Documentation August 25, 1991 Drive total kb used free % avail H(H):User 40192 37576 2616 S 7% JOIN C:\USR 23688 kbytes in files Efficiency = 69% 40192 33128 7064 18% <= FAT data 20102 18599 1503 7% <= STACVOL data 24210 kbytes in sectors Efficiency = 130% Here, the "kbytes in sectors" value is computed from adding together the file size for each file, ROUNDED to the nearest sector (512 bytes). The rounding is performed on a file-by-file basis, and represents the amount of space which the files would take up IF the cluster size was 512 bytes. This number is then divided by the space used by the STACVOL sectors, and the "Efficiency" of Stacker storage is reported. Note that this number is a bit conservative since the STACVOL "used" value includes space needed to store directories, whereas the "kbytes in sectors" value ignores directories. (If directories where included in the "kbytes in sectors" figure, the Stacker "Efficiency" would probably be less than 3 to 5 percent higher for most installations.) A NOTE ON Stacker The Stacker "compression ratio" (usually about 2:1) is a ratio be- tween the number of bytes used on the Stacker volume (with cluster [8k] granularity) and the number of bytes used in the STACVOL file (with 512 byte) granularity. This ratio is excellent for predicting how much more data will fit on a Stacker volume, but is artificially high in terms of actual "compression." Consider, for example, the compression ratios which would be calculated for small files if a cluster size of 16k or 32k was used! The Stacker "Efficiency" value is calculated assuming a "512 byte" cluster, and more accurately represents the amount of physical "compression" that the Stacker software performs. However, this value is artifically low in terms of the amount of data that can be stored on the Stacker volume compared with the amount of data that you could store on the same disk before Stacker was installed. This discrepancy is cause by the fact that before Stacker, the drive was using, at best, 2k clusters instead of the 512 byte "clusters" used for the "Efficiency" calculation. COMMAND-LINE OPTIONS: -s The "-s" option will remove the header and footer information from the output. Version 2.02 - 6 - DF Documentation August 25, 1991 COMMAND-LINE OPTIONS: -o The "-o" option will provide a more UNIX-like (cryptic) header, and display percentile information in terms of the percentage USED. COMMAND-LINE SWITCHES: USING / INSTEAD OF - In the default configuration, DF will accept BOTH "/" and "-" as command-line switches. PLEASE NOTE: When "/" is used as a switch, there MUST be a space before the switch. For example, "DF /a/S" will NOT work! Use "DF /a /S" or "DF /aS" instead. If you would like to restrict the switch to a specific character or set of characters, set the environment variable SWITCHES to that set of characters. The default is identical to SET SWITCHES=-/ If you SET SWITCHES=- you will be able to use the "/" as a directory delimiter in pathnames. If you SET SWITCHES=/ you will be able to use "-" as the first character in a filename. In any case, if you desire to use the switch characters in filenames, just preceed the filename with two switch characters (i.e., to specify the file "-file" use "DF -- -file"). ENVIRONMENT VARIABLES Two environment variable are available to store command-line options: DF_DEFAULT will be scanned for options if and only if no options or arguments appear on the command line. For example, if you SET DF_DEFAULT=-a, then typing "DF" is equivalent to typing "DF -a". DF_OPTS will force options regardless of the command-line. The only use for this option is "SET DF_OPTS=-o" which will force the old- style headings and percentile calculations. Note: These environment variables CANNOT be used to store pathnames. For information on the SWITCHES environment variable, see the pre- vious section. Version 2.02 - 7 - DF Documentation August 25, 1991 LICENSE INFORMATION DF is NOT in the public domain. Source code is NOT in the public domain and is NOT currently available. (However, in the future, source code may be distributed under a GNU-ish license.) Copies of DF for personal, corporate, or institutional use are FREE. This software may NOT be distributed commercially. This software comes with ABSOLUTELY NO WARRANTY: 1. This program is provided AS IS without any warranty, ex- pressed or implied, including, but not limited to, fitness for a particular purpose. 2. The author is not responsible for the consequences of use of this software. The author will be held harmless for any damages, either direct or consequential, that might arise from the use of DF. 3. The author reserves the right to change DF and its documentation without prior notice, with no obligation to the end user. CONTACTING THE AUTHOR Please send bug reports, comments, and suggestions to one of the following addresses: CompuServe: 72571,2241 InterNet: faith@cs.unc.edu OBTAINING FUTURE VERSIONS DF will be periodically updated, but since this is FREE software, the updates may be sporadic or non-existent. The author does not intend to spend a great deal of time updating/maintaining DF. The current version of DF will be available on CIS in the IBMHW forum, DL library 1 (Disk/Disk Utils); and from Channel 1 BBS. On the InterNet, DF will also be offered to, and may become avail- able via anonymous FTP from, wsmr-simtel20.army.mil (probably in <msdos.dskutl>). If DF becomes available from simtel20, it should Version 2.02 - 8 - DF Documentation August 25, 1991 also be available from sites which mirror simtel20, such as wuarchive.wustl.edu. TRADEMARKS UNIX is a registered trademark of AT&T. CompuServe is a registered trademark of CompuServe Incorporated. IBM is a registered trademark of International Business Machines Corporation. Stac is a registered trademark, and Stacker is a trademark of Stac Electronics. DESQview is a trademark of Quarterdeck Office Systems. Version 2.02 - 9 -