The information in this article applies to:
This information applies to both Microsoft DoubleSpace and Microsoft DriveSpace. For MS-DOS 6.00 and 6.20, use DBLSPACE in place of DRVSPACE for commands and filenames. SUMMARYDriveSpace uses sector allocation granularity even though you cannot see evidence of this in the Bytes Available On Disk value reported by CHKDSK. MORE INFORMATION
Since the file allocation table (FAT) system is cluster based, DriveSpace
uses its own FAT (which is called the MDFAT [Microsoft DriveSpace FAT]) to
achieve sector allocation. Each entry in the FAT corresponds to an entry in
the MDFAT, as well as a logical cluster of 8 kilobytes (K) for MS-DOS and
Windows 95 DriveSpace, or 32 K for Plus! DriveSpace 3. Each MDFAT entry
also corresponds to a sequence of sectors less than or equal to 8K (MS-DOS
and Windows 95 DriveSpace) or 32 K (Plus! DriveSpace 3).
Estimated Compression Ratio (ECR)When you run CHKDSK on a DriveSpace drive, it lists the number of used clusters in terms of uncompressed data. When it lists the number of unused clusters, it must specify some multiple of clusters based on how many compressed clusters it thinks can fit inside the actual free space. It does this by taking the ECR and multiplying it by the actual free space on the drive (in sectors) and then dividing that by the number of sectors in a cluster (16).As a result, free disk space can only be specified as a integral number of clusters. Additional query words: 6.00 6.20 Granular double space dblspace
Keywords : msdos |
Last Reviewed: November 16, 1999 © 2000 Microsoft Corporation. All rights reserved. Terms of Use. |