___________________________________________________________________________ STACKER NOTE STACKER NOTE Title: Stacker Drive Space Reporting STAC FAX Index #2602 - 2/10/93 ___________________________________________________________________________ Background. Use Stacker 2.0's SCHECK or Stacker 3.0's CHECK /D utility to see exactly how the space has been used in the Stacker drive. Here is an example of an SCHECK & CHECK /D report: Volume in drive C is STACVOL_DSK No errors found Stacker Drive Statistics: Stacker Drive STACVOL File Drive C: D:\STACVOL.DSK ------------------- -------------------- Total Bytes: 4,109,312 2,054,656 Bytes Used: 3,735,552 ( 91.2%) 1,846,272 ( 89.9%) Bytes Free: 373,760 ( 8.8%) 208,384 ( 10.1%) Stacker Drive Compression Ratio = 2.0:1 Projected Bytes Free = 373,760 What does it all mean? The Left Hand Column: This column displays "logical" data in the clusters on the Stacker drive. In this example, it tells us that there are enough allocation units (clusters) for 4 MB of data. There are enough clusters left to acomodate 373,760 bytes of data. The DOS CHKDSK program reports these numbers because it looks at allocation units. The Right Hand Column: This column shows the usage of actual physical hard disk space inside the STACVOL.DSK file. The Stacvol file contains all of the data and free space for the Stacker drive C:. It's name and location are shown in the column title. In our example, D:\STACVOL.DSK is 2 MB in size and has used all but 208,384 bytes of that 2 MB. Therefore, there are 208,384 bytes of physical free space left in D:\Stacvol.dsk. Compression ratio. The Stacker drive compression ratio indicates the average compression of the files in that drive. The compressibility of the files is generally dependent on their contents. 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 a "Non-Stacked" drive. (A 2.0:1 ratio is typical for an average mixture of files.) A drive full of graphics files may achieve an average compression of 8.0:1 or more. An 8.0:1 ratio would mean that the files are taking up 1/8 the space they would on a standard drive. Conversely, some files are already compressed, such as "zipped" files. Stacker will not attempt to compress previously compressed files, so they will bring down the overall compression ratio of the Stacked drive in which they reside. NOTE: 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 Stacked drive. It is determined by multiplying the physical free space (right side) by the compression ratio, OR by the number of clusters left unallocated (left side). The projected bytes free is limited to the smaller of these two values. In our example, physical space free multiplied by the compression ratio would be: 208,386 x 2.0 or 416,772 bytes. However, we only have 373,760 bytes worth of unallocated clusters. Since the projected bytes free is the smaller of these two numbers, it is 373,760. Fortunately, you can increase the number of allocation units by "growing" the drive. To grow the Stacker drive, run the Grow & Shrink utility from the STAC command assistant. "Growing" the drive in this example would increase the projected free space to 416,772. Notes: When the number for physical bytes free goes to zero, the drive is full. You cannot "grow" the drive to create more physical space. Also, if the drive is less than 12% full, the projected bytes free will equal the "logical" bytes free number (left column). ___________________________________________________________________________ Copyright 1993, Stac Electronics