TITLE: Stacker Statistics DOCUMENT ID: TID14920 DOCUMENT REVISION: 1 DATE: 25FEB94 ALERT STATUS: Yellow README FOR: NA NOVELL PRODUCT and VERSION: Novell DOS 7 ABSTRACT: NA --------------------------------------------------------------------- DISCLAIMER: THE ORIGIN OF THIS INFORMATION MAY BE INTERNAL OR EXTERNAL TO NOVELL. NOVELL MAKES EVERY EFFORT WITHIN ITS MEANS TO VERIFY THIS INFORMATION. HOWEVER, THE INFORMATION PROVIDED IN THIS DOCUMENT IS FOR YOUR INFORMATION ONLY. NOVELL MAKES NO EXPLICIT OR IMPLIED CLAIMS TO THE VALIDITY OF THIS INFORMATION. --------------------------------------------------------------------- ISSUE: This document is not designed to be an introduction to the Stacker portion of Novell DOS 7. Users who are new to Stacker should read the following references before reading this document: Novell DOS 7 User Guide: Chapter 12 "Disk Compression" Novell DOS 7 README.TXT Stacker section within the DOSBOOK online reference manual (Type DOSBOOK STACKER at the command line.) Novell DOS 7 offers three utilities for examining statistics on a Stacker drive: DIR, XDIR, and CHKDSK. Each of these utilities is specifically written to understand the internal structures of a Stacker drive. For a list and description of switches for these utilities refer to DOSBOOK or type the utility name followed by a /? (for example, DIR /?) at the command line. DIR The Novell DOS 7 DIR command has been written to give an accurate calculation of free space on a Stacker drive. Please see the Estimated Bytes Free section below for a description of how free space is calculated for a Stacker drive. XDIR The Novell DOS 7 XDIR command has been written to give compression ratios for each file on a compressed drive as well as an average compression ratio for the current directory. An example of an XDIR of the root directory follows: --a--- 355 8.0:1 2-24-94 9:32a c:autoexec.bat --a--- 73 8.0:1 2-18-94 10:32a c:autostac.bat ------ 56,081 1.4:1 1-26-94 7:00a c:command.com --a--- 306 8.0:1 2-23-94 11:43a c:config.sys rs--h- 27,880 1.4:1 1-26-94 7:00a c:ibmbio.com rs--h- 29,684 1.1:1 1-26-94 7:00a c:ibmdos.com DIRECTORY 2-18-94 10:02a c:nwclient DIRECTORY 2-18-94 10:02a c:nwcntl DIRECTORY 2-18-94 10:02a c:nwdos --a--- 4,768 8.0:1 1-26-94 7:00a c:nwdos.386 DIRECTORY 2-18-94 11:25a c:windows DIRECTORY 2-18-94 2:02p c:wpc20 DIRECTORY 2-18-94 2:00p c:wpwin60 total files 7 total bytes 119,147 disk free space 39,997,440 average compression ratio 1.6:1 To get an average compression ratio for the entire drive, use the command XDIR /S at the root of the Stacker drive to include all subdirectories. The average compression ratio figure obtained by doing an XDIR /S is representative of all the files on the drive. This figure is calculated by averaging the actual compression ratio for each file on the drive. An example of the last two lines of an XDIR /S follows: total files 1,304 total bytes 58,252,054 disk free space 39,997,440 average compression ratio 1.6:1 In the example, the average compression ratio of 1.6:1 is slightly below the expected compression ratio for the drive (fixed at 2.0:1). This suggests that the files on the Stacker drive are taking up slightly more room than expected. A Stacker drive is most efficient when the average compression ratio is as close to the expected compression ratio as possible. Ultimately the average compression ratio should not be much higher or lower than the 2.0:1 expected compression ratio. If the average compression ratio is much lower than 2.0:1 (as an example 1.2:1), an overabundance of poorly compressible data is on the drive. A user might consider taking files that have a compression ratio (found with XDIR /S) much lower than 2.0:1 off the drive. If the Stacker Drive Compression Ratio is much higher than 2.0:1 (as an example 8.0:1), an overabundance of highly compressible data is on the drive. A user might consider taking files that have actual compression ratio (found with XDIR /S) much higher than 2.0:1 off the drive. Note: The expected compression ratio is set at 2.0:1. Therefore, there are twice as many file allocation units in the Stacker FAT. A Stacked drive with files that compress at a higher ratio will use the allocation units at the same rate as files that compress at a lower ratio. Even though a drive may have a very high Stacker Drive Compression Ratio, such as 8.0:1, you will not be able to store any more data than the expected compression ratio of 2.0:1 allows. XDIR also gives accurate used and free space information on a Stacker drive. Please see the Estimated Bytes Free section below for a description of how free space is calculated for a Stacker drive. CHKDSK The Novell DOS 7 CHKDSK command used with a /D parameter will display space usage on a Stacker drive. An example CHKDSK /D follows: Volume STACVOL_DSK created Feb-18-1994 10:36 Checking cluster integrity... Stacker Drive Statistics: Stacker Drive STACVOL File Drive C: D:\STACVOL.DSK ---------------------- -------------------- Total Bytes: 162,914,304 61,506,048 Bytes Used: 61,329,408 ( 37.6%) 37,220,864 ( 60.5%) Bytes Free: 101,584,896 ( 62.4%) 24,285,184 ( 39.5%) Bytes Per Cluster: 4,096 2,048 Fragmentation Level = 0 Checking FAT integrity... 162,914,304 bytes total disk space. 61,440 bytes in 2 hidden files. 114,688 bytes in 24 directories. 61,153,280 bytes in 1302 user files. 39,997,440 estimated bytes free. 4,096 bytes in allocation unit. 39,774 total allocation units on disk. 24,801 available allocation units on disk. 655,360 total bytes of memory. 621,216 total bytes of free memory. 620,240 bytes in largest free memory block. Stacker Drive Drive C: This column of CHKDSK /D reports information based on the estimated compression ratio of all the files on the drive being 1.6:1. These statistics represent logical disk space as each figure represents how space on the Stacker drive would be used if this were a standard DOS formatted drive. In other words, this information is based on one cluster being the smallest allocable unit on the drive. Consider the method for reporting statistics in this column to be equal to what CHKDSK would display on any normal DOS formatted drive. STACVOL File G:\STACVOL.DSK This column of CHKDSK /D reports information based on actual physical disk space used by Stacker. In other words, its information is based on the amount of physical sectors (512 bytes) used within the STACVOL file after files have been compressed. Understanding that Stacker can store files at the sector level is important. This is unlike a normal DOS formatted drive, which stores files at the cluster level. Most third-party utilities are incapable of reporting actual physical disk space use on a Stacker drive. Estimated Bytes Free This number represents an estimate of the number of bytes free on a Stacker drive. Actual usable space may vary based on the compression ratio of the drive (see above note). This estimate is based on the lesser of the two values found using Method 1 and Method 2 that follow: Method 1: Estimated Bytes Free is found by multiplying the bytes free value in the STACVOL File column by the average compression ratio (found with XDIR /S). Although the average compression ratio is rounded off to tenths, the compression ratio used in the calculation is not rounded off. Method 2: Estimated Bytes Free is equal to the bytes free in the Stacker Drive column. Note: SETUP will allow you to expand or shrink a Stacker drive to increase or decrease the amount of space on the drive. However, when the number of bytes free in the STACVOL File column is zero, the drive is full. You cannot expand the drive to create more physical space. Also, if the drive is less than 12 percent full, the estimated bytes free will equal the bytes free value in the Stacker Drive column. --------------------------------------------------------------------- Any trademarks referenced in this document are the property of their respective owners. Consult your product manuals for complete trademark information. ---------------------------------------------------------------------