MS-DOS DoubleSpace/DriveSpace
Frequently Asked Questions
MS-DOS DoubleSpace/DriveSpace FAQ
Updated through 1997 only (dead links will not be fixed)
By , former MS-DOS Compuserve Support Professional
This page contains Frequently Asked Questions, and answers, about DoubleSpace and DriveSpace, the MS-DOS 6 disk compression software. PLEASE NOTE that MS-DOS, DoubleSpace and DriveSpace are obsolete and no longer supported by Microsoft.
These FAQs apply ONLY to MS-DOS disk compression.
These FAQs are based on about 7 years of attendance in the Compuserve MS-DOS Forum, answering these questions [through 1997].
DoubleSpace was distributed with MS-DOS 6.0 and 6.20. DriveSpace came with MS-DOS 6.22. They are virtually identical, so the names are used interchangeably here. Also "DxxSPACE" is used to refer to them collectively.
NOTE: I have almost NO experience with Windows 95/98 DriveSpace and DriveSpace-3 disk compression. Please don't ask me about problems with Windows 95/98 disk compression.
Please also see my disclaimer at the bottom of this page.
CONTENTS: Q1. I'm thinking about installing a compressed drive, but concerned about system performance. How does DriveSpace effect system speed? Q2. I've heard bad things about DoubleSpace/DriveSpace. Please comment. Q3. How does disk compression work? Q4. What is the Host Drive, and how does it get it's Letter? Q5. What is the size limit of a compressed drive? Q6. Where else can I learn about DriveSpace? Q7. How do I install Disk Compression? Q8. Will Windows work with a compressed drive? Q9. What is the difference between DoubleSpace and DriveSpace? Q10. Do some application programs not work with Compressed Drives? Q11. What does the error message "You must specify the host drive..." mean? Q12. When you say to do a "Clean Boot", what do you mean? Q13. Can I make a DoubleSpace compressed floppy diskette that is also bootable? Q14. I've uncompressed and removed my compressed drives, but DBLSPACE.BIN still loads into memory. How do I get rid of it? Q15. I'm trying to install DoubleSpace (DriveSpace) but I get the error message "no more drive letters reserved for DoubleSpace to use." What should I do? Q16. When I copy a file from my compressed drive to some other drive, is it still compressed? Q17. I'm trying to compress my "Hardcard" Drive, but having problems. What should I do? Q18. What should I do to optimize the performance and configuration of my compressed drive? Q19. Can I compress my RAM Drive? If so, how? Q20. Can I use 32-Bit File Access with Double/DriveSpace? Q21. I want to compress a floppy diskette, but DoubleSpace won't let me unless I compress a hard disk drive. What should I do? Q22. Please explain a typical DBLSPACE.INI or DRVSPACE.INI file. Q23. I'm trying to install DoubleSpace on a 1 Gigabyte Drive, but it doesn't seem to work. What's going on? Q24. I've installed DoubleSpace but now my Novell Network Login Drive isn't available. What should I do? Q25. I'm using DxxSPACE. Frequently something accesses my floppy drives for no apparent reason. What's going on? Q26. I need to change the Host Drive letter on my system. How do I do that? Q27. I need to start my system without loading DxxSPACE.BIN. How can I do that? Q28. When I boot my system the message "A CVF is Damaged" appears. What should I do? Q29. What is DoubleGuard? Q30. How do I safely defragment my uncompressed drive? Q31. Why is it recommended to run DBLSPACE /DEFRAGMENT /F followed by DBLSPACE /DEFRAGMENT? Q32. Do any programs interfere with DEFRAG of a compressed drive? Q33. I'm trying to resize my compressed drive but I receive the error message "Too Fragmented". What can I do? Q34. What are the Estimated Compression Ratio and Actual Compression Ratio? Q35. I'm trying to adjust the Estimated Compression Ratio of my compressed drive, but DxxSPACE won't let me. What should I do? Q36. I try to use DIR /C to find out the compression ratio for a file but there is no report. Why? Q37. How does DxxSPACE assign drive letters? Q38. I'm using a Lantastic? How do I installed DoubleSpace? Q39. My compressed C drive has disappeared. When I boot I only see COMMAND.COM and some Hidden DRVSPACE files. What do I do? Q40. My C drive is compressed and works fine, but my DRVSPACE.001 file will not mount. I want it to be the "D" drive, with "I" as the host. What do I do? Q41. What Microsoft support is available on-line and how do I reach it? Q42. When I start Windows 3.x I get a message about a corrupt Swap file. What's going on? Q43. How do I uncompress my compressed drive, and remove DoubleSpace from my system? Q44. I have a compressed drive. Should I use Write-Back Caching or not? Q45. I have a Bernoulli Drive. What should I know? Q46. I use MS-DOS 6.0 -- should I upgrade? Q47. Why can't I restore a older Backup with MS-DOS 6.22? Q48. Where can I find support files for MS-DOS?
Q1. I'm thinking about installing a compressed drive, but concerned about system performance. How does DriveSpace effect system speed? A: That depends on the PC and the specific operations being conducted. Operations that are very disk-write intensive can be slowed a bit. Using Write-back Caching alleviates most of this, but it has certain possible problems so some experts don't recommend it (others do). See also Question 44. The speed of your PC's processor is very important, as is the type of hard drive and its access speeds. On a fast processor disk compression can actually speed up some operations because the data is read in larger "chunks" with the disk drive speed being the actual limiting factor. On a slow processor, anything slower than an 80386 DX 33, you can expect to see some performance degradation overall. On an 80486 DX 33 and faster, you shouldn't see any significant difference except for those very write-intensive programs (which you can alleviate by keeping the program's data files on the uncompressed "Host Drive"). Overall, the figures I've seen indicate a performance reduction of 3-5% on average. This assumes that DxxSPACE is properly optimized (see other questions about that) and that a properly configured disk cache is in use. Of course 3-5% is a minor nuisance for those who have relatively small disk drives and need disk compression. Since DxxSPACE is exceptionally inexpensive, it has been very effective for many people while saving considerable hardware costs.
Q2. I've heard bad things about DoubleSpace/DriveSpace. Please comment. A: MS-DOS 6 and particularly DoubleSpace/DriveSpace have gotten a lot of bad press, especially when released in 1993. As far as I can personally tell, virtually all of it was based on speculation and rumor, plus an unfortunate trait in the press, including the technical computer press, to print almost anything if it will help sell magazines, newspapers, etc. My personal experience is that DoubleSpace/DriveSpace has been rock solid on my system and several others in my office for over 4 years now [this was as of 1997 when the systems were upgraded and disk compression was removed]. From the consensus of all of the reports on the Compuserve MS-DOS Forum, if your hardware is performing up to specifications, DoubleSpace/DriveSpace will performing flawlessly as it has on millions of systems, notwithstanding the unsubstantiated rumors you may have heard.
Q3. How does disk compression work? A: I'll summarize some things about DoubleSpace (MS-DOS 6.0/6.20) and DriveSpace (MS-DOS 6.22). The programs are identical as far as the user is concerned. A drive is "compressed" by DxxSPACE.EXE which creates a file into which it copies all the files on an existing drive and compresses them as it does so. The file is called a Compressed Volume File (CVF). It has the name DBLSPACE.000 (or DRVSPACE.000), or in some cases the extension will be ".001" (those are all numbers, not the letter "O"). The CVF will always be physically located in the root directory of the physical drive that has been compressed. It's a hidden file, so you would need to use DIR /A (or other DIR parameters) to see it. The CVF is managed and accessed as a "pseudo disk drive" by DBLSPACE.BIN (or DRVSPACE.BIN), which is a driver program that is installed along with MS-DOS itself and loads before CONFIG.SYS. The "BIN" file must be located in the root directory of the physical boot drive (always "C" as far as MS-DOS itself is concerned). Note that this is NEVER on a compressed drive. It too is a hidden file. In order for DBLSPACE.BIN to know what to do when the system is booted, there must be an initialization file called DBLSPACE.INI (or DRVSPACE.INI) in the same location -- root directory of the physical boot drive. DBLSPACE.INI must contain certain commands that DBLSPACE.BIN understands. Here's an example: MaxRemovableDrives=2 <= not strictly required but DxxSPACE will put it there LastDrive=H <= this is for DxxSPACE only, not like similar cmd in CONFIG.SYS MaxFileFragments=2600 <= the number may be much different ActivateDrive=H,C0 <= that's H, C Zero The last line is the key. It tells DBLSPACE.BIN to "mount" DBLSPACE.000 (the "zero" file) as DRIVE C, and internally re-letter the physical drive as "H". The re-lettered drive (which might be I or J or something else) is referred to as the Host Drive -- it is usually the physical boot drive (called "C" until DBLSPACE mounts the CVF). All to the above is necessary in order for the compressed drive to be available and accessible.
Q4. What is the Host Drive, and how does it get it's Letter? A: The Host Drive is the physical, uncompressed disk drive on which the Compressed Volume File of a compressed drive is stored. The Letter is assigned in DxxSPACE.INI. DxxSPACE.BIN manages the drive letters. In a typical installation, "C" will be the compressed drive, and "H" the Host Drive. Actually "H" is the uncompressed drive that was "C" before disk compression was installed. There is more about this in Chapter 5 of the MS-DOS 6.x User's Guide. And the following Microsoft Knowledgebase article also applies: How DoubleSpace Assigns the Host Drive Letter ID: Q94336
Q5. What is the size limit of a compressed drive? A: MS-DOS 6.x DoubleSpace and DriveSpace drives are limited to 512 megabytes. The MS-DOS limit for a drive using an 8K cluster size is 512 MB (65,536 clusters at 8192 bytes per cluster). Because MS-DOS DoubleSpace (and DriveSpace) supports only 8K clusters, a drive compressed with DoubleSpace is limited to 512 MB. If your compression ratio were 2:1 (optimistic), the physical size of the compressed volume file (CVF) would be 256 MB (plus a small overhead). To compress more of a physically large hard disk, you need to "Create (a) New" compressed drive using free space on the host. Run DxxSPACE.EXE and choose Create New from the Compress Menu. Use the remaining free space on the host to create a new empty compressed drive. There is an article available in the Microsoft Knowledgebase that has more information concerning the maximum size of a DoubleSpace drive. Search on the article ID listed below. Title: Largest Possible DoubleSpace Drive Is 512 MB ID: Q95533 This article does apply to MS-DOS 6.22 DriveSpace also. However, Windows 95 PLUS! "DriveSpace-3" has other, higher limits. Ask about this on Windows 95 Newsgroups or elsewhere.
Q6. Where else can I learn about DriveSpace? A: Read the MS-DOS 6 Users Guide Chapter 5, especially the section "Understanding Disk Compression". Read all of the on-line help articles that apply. Type HELP at a DOS prompt and select: DRVSPACE TIPS DRVSPACE DRVSPACE.SYS DRVSPACE.INI Be sure to read the <Notes> sections of each Help article. You should also look through the DriveSpace section of the README.TXT file in your DOS directory and on the first MS-DOS 6.x SETUP diskette. Addition information is in the following Articles (titles may have changed) from the Microsoft Knowledgebase. Search on the article ID's: listed below. Article Title: MS-DOS 6.2 DoubleSpace Questions and Answers Article ID: Q105072 Article Title: Optimizing DoubleSpace on Your Computer Article ID: Q97741 These Articles apply equally to DriveSpace.
Q7. How do I install Disk Compression? A: Here are some suggested procedures for safely installing DriveSpace (or DoubleSpace -- the procedures are the same): (1) Make a backup of your hard drive. This is a good idea in the absence of disk compression technology, but any time we install a program (such as disk compression software) that affects how information is read from or written to the disk, the necessity of a reliable backup cannot be overemphasized. (2) Run MS-DOS ScanDisk from MS-DOS 6.2x. Be sure to do a Surface Scan. DriveSpace will automatically run SCANDISK again, but you can't be too careful in this case. (3) Run DEFRAG on all logical drives. (4) Run DRVSPACE after clean starting your computer with a minimum CONFIG.SYS and AUTOEXEC.BAT file that loads only those device drivers required to boot your system and access the hard drive. REMark out all unnecessary drivers/TSRs or use F5 at "Starting MS-DOS..." to boot totally clean. (5) After DriveSpace is installed, perform regular and complete backups of your compressed drives.
Q8. Will Windows work with a compressed drive? A: Yes. Windows 3.1 and 3.11 run fine on a compressed drive. The only caveat is that a Windows Permanent Swap File must be on an UNcompressed drive, because Windows bypasses DOS to read and write directly to a permanent swap file. Windows 95 uses different procedures, but will install fine on a previously compressed drive. More information about using Windows 95 with compressed drives is available from Windows 95 sources. Do not attempt to install Windows NT on a system with a compressed drive.
Q9. What is the difference between DoubleSpace and DriveSpace? A: DriveSpace contains disk compression algorithms written entirely by Microsoft. MS-DOS 6.0 and 6.2 DoubleSpace users will see that DriveSpace is comparable to DoubleSpace performance and capacities. The DoubleSpace user interface look and feel has been retained with DriveSpace. As far as users are concerned, the only significant difference is the name. There is an article available in the Microsoft Knowledgebase that has further information on differences between DoubleSpace and DriveSpace. Search on the article ID: listed below. Title: MS-DOS 6.2 DoubleSpace Questions and Answers Article ID: Q105072
Q10. Do some application programs not work with Compressed Drives? A: Yes, a few programs, mainly older ones and some games, have problems with Compressed Drives. Generally the problem is that the application attempts to access files on disk drives directly, bypassing DOS. This doesn't work because the files are not where they are expected to be. There is an article available in the Microsoft Knowledgebase that has further information on this. Search on the article ID: listed below. Title: Applications That Don't Run on DoubleSpace-Compressed Drives ID: Q97740
Q11. What does the error message "You must specify the host drive..." mean? A: The error message "You must specify the host drive..." is coming from SMARTDRV, not DxxSPACE. Edit your AUTOEXEC.BAT and correct the SMARTDRV line to either: (1) omit entirely the reference to the DoubleSpace drive (probably C), or (2) change the reference to read the Host Drive, probably H. With no drive letter(s) indicated SMARTDRV will properly figure out how to cache the host drive, and thus the compressed drive indirectly. This is the syntax most of people use: (load high info) C:\DOS\SMARTDRV.EXE (optional size parameters) There is an article available in the Microsoft Knowledgebase that has further information on this exact message, cause and solution. Search on the article ID: listed below. Title: SMARTDRV Err Msg After Installing DBLSPACE: You Must Specify ID: Q105181
Q12. When you say to do a "Clean Boot", what do you mean? A: A "clean boot" starts your system with a minimum (or no) device drivers and resident programs loaded into memory, thus providing the "cleanest" possible memory situation. You can boot clean several ways. 1. If you have MS-DOS 6.0 or later, press F5 during boot up just before or when the announcement "Starting MS-DOS..." appears on the screen. This causes MS-DOS to skip CONFIG.SYS/AUTOEXEC.BAT. 2. Rename CONFIG.SYS/AUTOEXEC.BAT to something else, say CONFIG.SAV/AUTOEXEC.SAV. 3. Move CONFIG.SYS/AUTOEXEC.BAT to a different directory, temporarily. 4. Alternatively, if your computer requires a Driver program in CONFIG.SYS in order to boot, then copy the existing files to a different directory and use the following minimum setup CONFIG.SYS: DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS DOS=HIGH,UMB FILES=20 BUFFERS=20 {mandatory driver here with DEVICEHIGH= if possible} If you have MS-DOS 6.0 or higher, see HELP CONFIG.SYS for more info. The Microsoft Knowledgebase has an article which discusses a clean boot for Windows 3.x. Search on the article ID: listed below. Article ID Q87290 Title: What Is a Clean Boot for Windows 3.1?
Q13. Can I make a DoubleSpace compressed floppy diskette that is also bootable? A: Yes. There is a Microsoft Knowledgebase article on creating a bootable DBLSPACE diskette. Search on the article ID: listed below. Title: MS-DOS: Making a Bootable DoubleSpace Floppy Disk ID: Q97455
Q14. I've uncompressed and removed my compressed drives, but DBLSPACE.BIN still loads into memory. How do I get rid of it? A: Delete the DBLSPACE.INI file in the root directory of your boot drive. It's a Hidden/System/Readonly file. Use DIR /A to see it. Use ATTRIB to change its attributes so you can DEL it, or use DELTREE DBLSPACE.INI to delete it directly. DBLSPACE.BIN (or DRVSPACE.BIN) will only load if there is an INI file there. Normally, DxxSPACE.EXE removes the INI file when it accomplishes the uncompressing of the drive. This applies to MS-DOS 6.20 and higher only.
Q15. I'm trying to install DoubleSpace (DriveSpace) but I get the error message "no more drive letters reserved for DoubleSpace to use." What should I do? A: This error occurs when not enough drive letters have been made available to DoubleSpace, or your DBLSPACE.INI file is missing or corrupted. To work around this problem, follow the appropriate procedure below. If there are no drive letters available for DoubleSpace to mount a drive, use the following procedure to increase the "Last drive reserved for DoubleSpace's use" setting. 1. To run DoubleSpace, type "DBLSPACE" (without the quotation marks) at the command prompt. 2. From the Tools menu, choose Options. 3. Increase your "Last drive reserved for DoubleSpace's use" setting by at least one letter. If your DBLSPACE.INI file Is Missing or Corrupted, you can create a C:\DBLSPACE.INI file (where C is your startup disk) with a text editor such as MS-DOS Editor. The DBLSPACE.INI file should contain the following two lines: MaxRemovableDrives=2 <= 1 or 2 depending on home many diskette drives you have LastDrive={x} <= {x} = one letter beyond your last logical drive letter. Your drive should now mount normally with a DBLSPACE /MOUNT command. For more information on this command, type "help DBLSPACE /MOUNT" (without the quotation marks) at the MS-DOS command prompt and then press ENTER. There is an article available in the Microsoft Knowledgebase that has further information on this. Search on the article ID: listed below. Title: DoubleSpace Err Msg: "There Are No More Drive Letters" ID: Q93582
Q16. When I copy a file from my compressed drive to some other drive, is it still compressed? A: Files are compressed only when actually in the Compressed Volume File of a DBLSPACE or DRVSPACE compressed drive. At all other times they are in their normal state. See Chapter 5 of the MS-DOS User's Guide, especially the section about Understanding Disk Compression, for an explanation of how Disk Compression works and how information is stored in a CVF. When your programs load into RAM and then read data files, they are automatically UNcompressed as needed. It is all "invisible" to you, which is a reason for using it in the first place. You need to take NO special actions to make this happen. Please also see HELP DBLSPACE TIPS and HELP DBLSPACE, particularly the <Notes> section. You can see these on-line Help articles by typing HELP {keyword} at any MS-DOS prompt. See also the Microsoft Knowledgebase article listed below. Search on the article ID: listed below. Title: MS-DOS 6.2 DoubleSpace Questions and Answers ID: Q105072
Q17. I'm trying to compress my "Hardcard" Drive, but having problems. What should I do? A: The following article in the Microsoft Knowledgebase explains how to mount a Hardcard that does not mount automatically. Search on the article ID: listed below. Title: DoubleSpace Does Not Mount Hardcard Drive Automatically ID: Q97578 Generally you would just add the "DBLSPACE /MOUNT {drive}:" command to your AUTOEXEC.BAT to mount that drive.
Q18. What should I do to optimize the performance and configuration of my compressed drive? A: The following article from the Microsoft Knowledgebase contains some tips for optimizing DoubleSpace. Search on the article ID: listed below. Title: Optimizing DoubleSpace on Your Computer ID: Q97741
Q19. Can I compress my RAM Drive? If so, how? A: There are two articles in the Microsoft Knowledgebase which describe the automation of RAMDrive compression and give tips for doing so. Search on the article ID's listed below. Title: Automating RAMDrive Compression with DoubleSpace ID: Q95633 Title: RAMDRIVE.SYS Should Precede DBLSPACE.SYS in CONFIG.SYS ID: Q95861
Q20. Can I use 32-Bit File Access with Double/DriveSpace? A: There are a couple of articles available in the Microsoft Knowledgebase that have information on using 32-Bit File Access with DoubleSpace/DriveSpace. Search on the article ID's listed below. Title: 32-Bit File Access Requires MS-DOS 6.2 DoubleSpace ID: Q106248 Title: WFWG Err Msg: The 32-Bit File System Cannot Be Used When... ID: Q109623 Note the DriveSpace meets the requirements of the first article listed above.
Q21. I want to compress a floppy diskette, but DoubleSpace won't let me unless I compress a hard disk drive. What should I do? A: What you'll need to do to get this to work is to fool DoubleSpace into thinking it's installed on the hard drive. There is an article in the Microsoft Knowledgebase that explains how to do this. Search on the article ID: listed below. Title: Can't Compress Floppy Drive Without DoubleSpace Installed ID: Q100763 The basic trick is to create a DBLSPACE.INI file using any text editor and insert the following lines: LastDrive=(the last drive letter on your system + 2) MaxRemovableDrives=(number of diskette drives, 1 or 2) Save this file as C:\DBLSPACE.INI. Reboot and you will be able to use DBLSPACE to compress and read compressed floppies.
Q22. Please explain a typical DBLSPACE.INI or DRVSPACE.INI file. A: Here is the contents of a typical DxxSPACE.INI file: MaxRemovableDrives=2 FirstDrive=D LastDrive=I MaxFileFragments=2000 AutoMount=1 ActivateDrive=I,C0 Here's an explanation: MaxRemovableDrives=2 -- 2 diskette drive on the system. FirstDrive=D -- first drive letter that DxxSPACE may use; this is used internally by DxxSPACE.BIN only. LastDrive=I -- last drive letter that DxxSPACE may use; if DxxSPACE runs out of drive letters, an error message will be displayed. MaxFileFragments=2000 -- maximum number of file fragments that DxxSPACE will handle within a CVF. The number will vary. Use 2000 or more if setting this manually. AutoMount=1 -- Automatic mounting of removable compressed drives is enabled (1) or disabled (0). If you don't use compressed removable drives, set this to 0 (zero). ActivateDrive=I,C0 -- (I,Czero) Tells DxxSPACE.BIN to mount the CVF which extension ends with zero (.000) as compressed drive "C", and use "I" as the host drive letter. There may be more than one line like this. See also HELP DBLSPACE.INI or HELP DRVSPACE. Type this command from a DOS prompt.
Q23. I'm trying to install DoubleSpace on a 1 Gigabyte Drive, but it doesn't seem to work. What's going on? A: For internal technical reasons, DoubleSpace and DriveSpace have problems running on partition sizes between 1.028 GB and 1.153 GB. There is detailed information about this in the Microsoft Knowledgebase. Search on article ID: Q119072.
Q24. I've installed DoubleSpace but now my Novell Network Login Drive isn't available. What should I do? A: The following article in the Microsoft Knowledgebase gives a step-by-step description on how to resolve your problem. Search on the article ID listed below. Title: Novell Login Drive Not Available After Installing DoubleSpace ID: Q97565
Q25. I'm using DxxSPACE. Frequently something accesses my floppy drives for no apparent reason. What's going on? A: MS-DOS 6.2x contains a feature called AutoMount. What you are seeing is DxxSPACE checking to see if a floppy needs to be automatically mounted. If this feature isn't desired it can be turned off. From the DOS prompt outside of Windows run DxxSPACE. Select Tools, then Options. Un-check "Enable Automounting".
Q26. I need to change the Host Drive letter on my system. How do I do that? A: If you have MS-DOS 6.2 or later , you can use the DBLSPACE /HOST command to change the host drive letter. See HELP DBLSPACE and HELP DBLSPACE /HOST. The basic syntax is: DBLSPACE C: /HOST=x (where X is the desired Host Drive letter) The desired Host Drive letter must be "available to DoubleSpace". Use DBLSPACE /LIST to see the list. However, if you have MS-DOS 6.0 (which you should not; see the Question about upgrading from MS-DOS 6.0), the procedure is more complicated and fraught with the possibility of error. Here is the procedure: Normally it's a good idea to remove MS-DOS 6.0 DoubleSpace and re-install to change the host drive designation. But, if you'd like to, you can edit the DBLSPACE.INI file to change the drive. NOTE: This can be dangerous if done improperly so I'd recommend that you have a backup available just in case. What you're probably going to want to do is move the host drive designation lower, to E: for example, instead of H:. First log onto drive H. 1) issue the command ATTRIB -S -H -R DBLSPACE.INI 2) issue the command EDIT DBLSPACE.INI 3) change the LastDrive line to E instead of H (this is LastDrive for DoubleSpace only) 4) change the ActivateDrive line from H to E example: from: ActivateDrive=H,C0 to: ActivateDrive=E,C0 5) save the changes and exit from EDIT 6) reboot (You do not need to restore the Attributes on DBLSPACE.INI. That will be done automatically when the compressed drive is mounted during the reboot process.)
Q27. I need to start my system without loading DxxSPACE.BIN. How can I do that? A: You can boot your system (with MS-DOS 6.2x) without the DxxSPACE.BIN driver by pressing CTRL-F8 during startup at the point "Starting MS-DOS..." appears. When you do this any compressed drives that you have will not be available to you until you re-boot your system. If your problem is that conventional memory is tight, you can also move DxxSPACE.BIN into Upper Memory using the DBLSPACE.SYS program and your memory manager's Upper Memory manager (e.g. EMM386.EXE). See HELP DxxSPACE.SYS for more info on that, and HELP MEMMAKER also. Also see the MS-DOS Users Guide (Chapter 6) regarding memory management.
Q28. When I boot my system the message "A CVF is Damaged" appears. What should I do? A: There are a couple of articles available in the Microsoft Knowledgebase that have further information on the CVF is Damaged message and CHKDSK. Search on the article ID's listed below. Title: DBLSPACE /CHKDSK Stops (Hangs) with Cross-Linked Files ID: Q97884 Title: Corrupted DBLSPACE.EXE May Cause a "CVF Is Damaged" Error ID: Q103388 If using MS-DOS 6.0, see also Section 7.17 of the README.TXT file in your C:\DOS directory. You should also run MS-DOS 6.2x SCANDISK if you have access to it. If not, you should see the Question here about upgrading to MS-DOS 6.22.
Q29. What is DoubleGuard? A: DoubleGuard is a program that constantly checks the validity of the memory DoubleSpace (or DriveSpace) is using. If another program were to change the data DoubleSpace is storing in memory, the data on your drive could be damaged. To prevent other programs from damaging your data, DoubleGuard shuts down your computer immediately if it detects any unauthorized changes to DoubleSpace's memory. See also section 7.19 of the MS-DOS 6.2x README.TXT file, which is in your DOS directory. To find out the meaning of DoubleGuard warnings you should look at the following article in the Microsoft Knowledgebase that describes the errors. Search on the article ID: listed below. Title: DoubleSpace DoubleGuard Error Codes ID: Q106126 If the errors continue you should remove any memory resident software and continue working to see if that software had anything to do with the errors.
Q30. How do I safely defragment my uncompressed drive? A: The basic idea is discussed in section 7.12 of the README.TXT file (in your DOS directory) for MS-DOS 6.2x. It reads in part, "If you want to fully defragment your uncompressed drive, you must first unmount all compressed drives located on the uncompressed drive, remove all their attributes, and then use DEFRAG or another defragmenter." To do that: (1) you must boot your system from a drive not involved, usually A, with a copy of the DEFRAG program on the boot drive. (2) You must unmount the compressed volume(s) on the drive you wish to defrag. The easiest way is probably to press CTRL-F8 when "Starting MS-DOS..." appears, which prevents DRVSPACE.BIN from loading, and thus the CVF(s) are not mounted. (3) Then use the ATTRIB command (see HELP ATTRIB) to remove the Hidden/System/Readonly attributes from the CVF(s) on the drive you want defrag (ATTRIB must be available on the boot disk). You may also wish to remove these attributes on the other DxxSPACE files so that they can be moved by the DEFRAG program. (4) Then run DEFRAG on that drive (see HELP DEFRAG). The CVF is treated like any other file. Please note that some free space is needed (I don't know how much and it will vary) and you must be careful to remove any "unmovable" files such as those created by IMAGE or MIRROR (just delete them). (5) When the DEFRAG is completed, don't forget to add the attributes to the CVF's and other files on which you may have changed attributes. Please note that unless a CVF is severely fragmented, you can't actually expect to see much if any performance improvement as a result of the above.
Q31. Why is it recommended to run DBLSPACE /DEFRAGMENT /F followed by DBLSPACE /DEFRAGMENT? A: There is an excellent article available in the Microsoft Knowledgebase that has specific information on this question. Search on the article ID: listed below. Title: Difference Between DEFRAG and DBLSPACE /DEFRAGMENT ID: Q94357
Q32. Do any programs interfere with DEFRAG of a compressed drive? A: Here is a partial list of problem files that interfere with DEFRAG'ing of a DoubleSpace or DriveSpace compressed drive: Microsoft MS-DOS Mirror MIRROR.COM MIRORSAV.FIL Central Point Mirror MIRROR.COM MIRORSAV.FIL Symantec Norton Image IMAGE.EXE IMAGE.IDX Symantec Norton Format Recover FR.EXE FRECOVER.IDX Microsoft MS-DOS 5.0 Undelete MIRROR.COM PCTRACKR.DEL Microsoft MS-DOS 6.0/6.2 Undelete - Delete Tracker UNDELETE.EXE PCTRACKR.DEL - Delete Sentry UNDELETE.EXE CONTROL.FIL Central Point Undelete - Delete Tracker UNDELETE.EXE PCTRACKR.DEL - Delete Sentry UNDELETE.EXE CONTROL.FIL Other utility programs similar to the ones above are also likely to interfere with the DEFRAG of a compressed drive.
Q33. I'm trying to resize my compressed drive but I receive the error message "Too Fragmented". What can I do? A: You may have an unmovable file or files at the "end" of your drive's space. Generally these are files saved in the root directory by MIRROR or IMAGE which store information about your partition table, etc. DEFRAG cannot move these files out of its way since they are marked as SYSTEM, HIDDEN, or READONLY. Use HELP DIR and HELP ATTRIB for more info about the commands you need to use to see them and change their attributes so that you can DELete them. If the problem is not being caused by a delete-tracking program placing a system file at the end of your DoubleSpace drive, and DEFRAG /H /Q <x>: (where /Q is an undocumented switch which means "do a quick defrag of the free space on a DoubleSpaced drive") does not correct the problem, edit the DBLSPACE.INI file and increase the MaxFileFragments setting by using the following steps: 1. Remove the Read-Only, System, and Hidden file attributes on the DBLSPACE.INI file. For example, if drive H is your host drive, type the following at the MS-DOS command prompt and press ENTER: ATTRIB {host_drive}:\DBLSPACE.INI -r -s -h 2. Using MS-DOS Editor, edit the DBLSPACE.INI file and increase the value for MaxFileFragments; 2000 is a good number to try. 3. Save the DBLSPACE.INI file and quit MS-DOS Editor. 4. Use the ATTRIB command to reset the file attributes on DBLSPACE.INI. For example, type the following command and press ENTER: ATTRIB {host_drive}:\DBLSPACE.INI +r +s +h 5. Restart your computer and try to resize the drive. If you still cannot resize the drive, you may have a bad sector on your host drive near the end of the DoubleSpace CVF. Decreasing the size of a compressed drive causes the file allocation table (FAT) to be truncated. If a FAT entry past the truncation point is marked anything but "free," DoubleSpace displays the error noted above. To maintain compatibility with copy-protection schemes and programs that use clusters marked as "bad" to store data, DoubleSpace does not shrink the FAT past a "bad" cluster. If you are not using any copy-protected software, you can work around this problem by unmounting the DoubleSpace-compressed drive and running a disk scan program on the host drive. With MS-DOS 6.2, you can simply run ScanDisk on the host drive without unmounting the DoubleSpace-compressed drive. For example, type "SCANDISK <host drive>: /surface" (without the quotation marks) at the MS-DOS command prompt and then press ENTER.
Q34. What are the Estimated Compression Ratio and Actual Compression Ratio? A: The free space on your compressed drive is an estimate based on Double/DriveSpace's Estimated Compression Ratio (ECR). Some files compress much more than others. A large dBASE data base will compress very well. A PKZIP "ZIP" archive will not compress at all. See the following Microsoft Knowledgebase articles for more information on these issues: Title: "DoubleSpace Estimated & Actual Compression Ratios" Article ID: Q96391 Title: MS-DOS Err Msg with DoubleSpace: Insufficient Disk Space" Article ID: Q100911
Q35. I'm trying to adjust the Estimated Compression Ratio of my compressed drive, but DxxSPACE won't let me. What should I do? A: There is an article available in the Microsoft Knowledgebase that has further information. Search on the article ID: listed below. Title: Cannot Lower Estimated Compression Ratio with DoubleSpace ID: Q96386
Q36. I try to use DIR /C to find out the compression ratio for a file but there is no report. Why? A: The DIR /C command does not report a compression ratio for a file if one of the following is true: - The Microsoft DoubleSpace FAT (MDFAT) is damaged. - The file is open in another Windows virtual machine (VM), and the MDFAT has not been updated. - The file was created by Microsoft Backup (or Microsoft Backup for Windows). To work around this problem, check the file compression ratio in File Manager or run ScanDisk. The fact that a file does not have a compression ratio does not affect the ability of DoubleSpace to calculate an actual compression ratio (ACR) for the whole drive.
Q37. How does DxxSPACE assign drive letters? A: The FirstDrive setting specifies the lowest drive letter available for use by DoubleSpace. FirstDrive is set by DBLSPACE.EXE each time it modifies the DBLSPACE.INI file. Do not change the FirstDrive variable yourself. There is an article available in the Microsoft Knowledgebase that has further information. Search on the article ID: listed below. Title: Order in Which MS-DOS Assigns Drive Letters ID: Q51978
Q38. I'm using a Lantastic? How do I installed DoubleSpace? A: There is an article available in the Microsoft Knowledgebase that has further information concerning Lantastic and DoubleSpace. Search on the article ID: listed below. Title: Using DoubleSpace with Lantastic ID: Q97573
Q39. My compressed C drive has disappeared. When I boot I only see COMMAND.COM and some Hidden DRVSPACE files. What do I do? A: Please try the following: Use your MS-DOS 6.22 Upgrade disks and run SETUP /F to create a Startup disk for the A: drive. Boot with the Startup disk in a: and use the MS-DOS Edit command to create a DRVSPACE.INI file with the following lines: MaxRemovableDrives=2 LastDrive=H MaxFileFragments=2600 ActivateDrive=H,C0 <= "H","C" ZERO Save the file to the current (uncompressed) C drive, root directory, and reboot to the hard drive. IF the CVF still fails to mount, place the Startup disk in A: and from the A: prompt enter the command: DBLSPACE /MOUNT C:
Q40. My C drive is compressed and works fine, but my DRVSPACE.001 file will not mount. I want it to be the "D" drive, with "I" as the host. What do I do? A: First, make sure that DRVSPACE.BIN is located in the root directory of the hard drive, the current "C" drive. It's a hidden files, so use DIR /A to see it. Next, type DRVSPACE alone at a DOS prompt. Check the Drive menu for a MOUNT command and try to mount the DRVSPACE.001 file. If DRVSPACE finds the 001 file, it will ask you how to mount it and you can tell it to use "D". DRVSPACE will update it's INI file and the next time you re-boot, the drive will be automatically mounted. In the unlikely event that that doesn't work, using any text editor you have, edit the DRVSPACE.INI file in your C:\ directory. You'll need to use the ATTRIB command to change it's attributes so you can see and edit it. See HELP ATTRIB. Make sure the file has a line like this: ActivateDrive=D,H1 Save the DRVSPACE.INI file to the root of C: and reboot. If the compressed drive does not mount, enter the command: DRVSPACE /MOUNT D:
Q41. What Microsoft support is available on-line and how do I reach it? A: Electronic Information Services are offered as a low cost alternative to direct person-to-person support. All U.S. and Canadian Microsoft customers have 24-hours-a-day, seven-days-a-week access to Microsoft's wide range of no-cost and low-cost Electronic Information Services options, including the following: Microsoft FastTips Toll-free, 24-hours-a-day, seven-day-a-week access to automated information about key Microsoft products. Access common question and answers as well as technical articles, via voice, fax, and U.S. mail. FastTips for Desktop Applications (800)-936-4100 FastTips for Personal Operating Systems (800)-936-4200 FastTips for Development Products (800)-936-4300 FastTips for Advanced Systems (800)-936-4400 Microsoft Knowledgebase A Primary Microsoft product information source. Database of more than 30,000 detailed articles with technical information on Microsoft products, bug lists, fix lists and more. Accessible via this link: Microsoft Knowledgebase. Microsoft Download Service Access to the Microsoft Electronic Technical Library, containing sample programs, device drivers, patches, software updates and programming aids. Direct access to Microsoft Download Library (MSDL) via modem through the Microsoft BBS service at (206) 637-6735 or 637-9009. Available 7 days per week, 24 hours per day including holidays. Microsoft product information and download files are also available from: FTP - ftp://ftp.microsoft.com WWW - http://support.microsoft.com/directory/ and from The Microsoft Network and Microsoft sponsored Newsgroups on the Internet.
Q42. When I start Windows 3.x I get a message about a corrupt Swap file. What's going on? A: The Windows Permanent Swap file must be located on an UNcompressed disk volume. Press "Y" to delete the corrupt Swap file, then use the Control Panel to create a new one, but this time do NOT put it anywhere on the Compressed Volume (usually your C drive). If you don't know where your UNcompressed drives are use this command from the DOS prompt: DxxSPACE /LIST to get a list of all drives.
Q43. How do I uncompress my compressed drive, and remove DoubleSpace from my system? A: (1) If you have MS-DOS 6.2 or later, then just enter the command DBLSPACE (or DRVSPACE) at a DOS prompt. I recommend you boot "clean" first, without unnecessary drivers and TSRs. When the DBLSPACE menu system appears, select the Drive Menu, and the DELETE command. Follow the prompts. Or, you can use the command line interface. Enter the command DBLSPACE /UNCOMPRESS {drive-letter} at a DOS prompt. Be sure to read the on-line Help about this command first. To do that, enter the following at a DOS prompt: HELP DBLSPACE /UNCOMPRESS Be sure to read the Notes section of this Help by selecting <Notes> at the top of the screen. (2) If you have MS-DOS 6.0, see the README.TXT file in your DOS directory, section 7.6, which describes in detail how to uncompress and remove DBLSPACE. If, for some reason you do not have the README.TXT file, there is an article available in the Microsoft Knowledgebase that describes the procedures to remove DoubleSpace and preserve your files. Search on the article ID: listed below. Title: How to Remove DoubleSpace and Preserve Your Files ID: Q96250 (3) Related information (MS-DOS 6.2 or later): As DoubleSpace uncompressed files and copies them to the uncompressed drive, it re-sizes the uncompressed drive (periodically as necessary) to make the compressed drive smaller and the uncompressed drive larger. In order to uncompress a drive: (1) You need at least as much total physical space on the hard drive volume as the size of the files to be uncompressed, and (2) A little extra space (a couple of megs or so) for DoubleSpace to use for its working space. This space needs to be free space at the beginning of the process. (3) No duplicate (full) filenames on the compressed and uncompressed drive. X.Y can exist on both drives if not in the same directory, but if X.Y is on both drives in the same directory (usually the root) this must be corrected before the process can continue.
Q44. I have a compressed drive. Should I use Write-Back Caching or not? A: Write-Back Cache is potentially dangerous since there is a longer time slice when data has been written to the cache but not yet physically written to the disk drive. If something interrupts the system or writing process (a power failure, inadvertent power down, some system lockups, etc.) the data in the cache is lost -- and potentially the disk file is corrupted. This can be somewhat worse on a Compressed Drive, because the data in the cache may contain information related to how files are stored, and if it is corrupted, the drive itself may become difficult or impossible to access. Write-Back Cache is fairly safe if power failures are very rare and you never turn your system off, and if you aren't experiencing system lock ups. However, if is sufficiently unsafe that the latest version of SMARTDRV comes with Write-Back Cache OFF by default (the "/X" parameter). If you are using SMARTDRV 4.2 (or later) you can use the /X parameter to be sure that it is turned off. With SMARTDRV 4.1, you need to specify the drive letter (without + or -) on the SMARTDRV command line in order to turn off Write-Back Cache. See the on-line help. At any DOS prompt, type: HELP SMARTDRV Please note that the problem with Write-Back Cache is not unique to SmartDrive (or to a compressed drive system). It is a potential problem for any cache. Also note that the latest versions of SmartDrive, including 5.0 and 5.1 with MS-DOS 6.20/6.21/6.22, also include some additional protection built in. For example, the cache is written before the MS-DOS prompt returns when you exit a program. Caution: You should NEVER turn the system off to "exit a program" or before making sure that the system has finished writing data. Always wait a few seconds after finishing your work/play before turning it off. Better yet, don't turn it off. My systems have been on for years, except for a couple of visits to the shop for hardware upgrades.
Q45. I have a Bernoulli Drive. What should I know? A: Please see the following Microsoft Knowledgebase articles: Title: DoubleSpace Mounts Bernoulli Disk as Non-Removable ID: Q105256 Title: Cannot Remount DoubleSpace Drive (ASPIDRVR.SYS and DOSOAD.SYS) ID: Q109251 Title: Err Msg: 'DoubleSpace Cannot Continue...' with Bernoulli ID: Q96030 Title: Bernoulli Drive Doesn't Mount with DoubleSpace Loaded ID: Q96087 Search on the article ID.
Q46. I use MS-DOS 6.0 -- should I upgrade? A: YES! I VERY STRONGLY urge you to upgrade your MS-DOS version. It is a very inexpensive and VERY significant upgrade, particularly for DoubleSpace users. There is an article available in the Microsoft Knowledgebase that has information about that. Search on the article ID listed below. Article Title: Why Should I Install MS-DOS 6.22? ID: Q105831 You can obtain the MS-DOS 6.22 STEPUP.EXE file (note that the file name is STEPUP.EXE, not SETUP.EXE) from some U.S. software stores for under US$10, and from the following on-line sources for the cost of downloading a 2.5+ megabyte file. FTP - ftp://ftp.microsoft.com WWW - http://support.microsoft.com/directory/
Q47. Why can't I restore a older Backup with MS-DOS 6.22? MS has made MS-DOS 6.0/6.20's DBLSPACE.BIN file available for downloading for use by those who have MS-DOS 6.22's MXBACKUP and no earlier copy of MS-DOS. Now folks will be able to restore compressed backups made under 6.0/6.20. There is an article available in the Microsoft Knowledgebase that has detailed information about this. earch on the article ID listed below. Article Title: Cannot Restore DoubleSpace Compressed Backup with MS-DOS 6.22 ID: Q148479
Q48. Where can I find support files for MS-DOS? Microsoft support files for MS-DOS can be downloaded from several sources. Please see the following article in the Microsoft Knowledgebase. Search on the article ID listed below. ARTICLE-ID: Q119591 TITLE : How to Obtain Microsoft Support Files from Online Services
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The information on this page is offer "as-is" with no guarantees that it will be completely accurate. Microsoft Corporation and the Compuserve Information Service had no part in the creation of this file. Opinions expressed are those of the author only.