| DoubleSpace Tips |
|
| This topic provides tips for getting the most out of DoubleSpace, and also |
| answers some common questions about DoubleSpace. For additional information |
| about DoubleSpace, see the "Freeing Disk Space" chapter in the MS-DOS 6 |
| User's Guide, or see the DBLSPACE command. |
|
| What does DoubleSpace do? |
|
| DoubleSpace is a disk-compression program. It stores more files in less |
| space by storing those files more efficiently. Most files are stored fairly |
| inefficiently -- somewhat like a sponge that has a lot of air holes in it. |
| When you squeeze a sponge, it becomes temporarily smaller; but when you let |
| go of it, the sponge returns to its original shape and size. When you |
| compress a drive, DoubleSpace "squeezes" the files on that drive until they |
| are as small as possible -- just like squeezing a sponge. A file stored on a |
| compressed drive stays "squeezed" until you use it. When the file is loaded |
| into memory, DoubleSpace uncompresses the file so that it returns to its |
| original size, just as a sponge does when you let go of it. When you're |
| finished using the file, DoubleSpace "squeezes" it again and stores it back |
| on the compressed drive. |
|
| When should I use DoubleSpace? |
|
| You should use DoubleSpace if you are running low on disk space and don't |
| want to invest in a larger hard disk drive. DoubleSpace can dramatically |
| increase your available disk space. However, because DoubleSpace uses at |
| least 33K of memory, it makes sense not to install DoubleSpace unless you |
| need it. |
|
| How does DoubleSpace "squeeze" a file? |
|
| Most files contain a lot of repeated data. When DoubleSpace finds repeated |
| data in a file, it retains the first occurrence of that data, and replaces |
| any other occurrences of that data with a cross-reference to the first |
| occurrence. The cross-reference takes less space than the original data. |
|
| For example, the following phrase includes the repeated data "at ": |
|
| The fat cat sat up. |
|
| DoubleSpace compresses this sentence by replacing the repeated "at " |
| characters (including the space) with a cross-reference to the first "at ". |
| In this example, cross- references are represented by the # character: |
|
| The fat c#s#up. |
|
| Why does DoubleSpace compress some files more than others? |
|
| Some files contain more repeated data than others. For example, program |
| files are usually compiled so that they are stored as efficiently as |
| possible; program files are typically not as compressible as some other |
| types of files. Bitmap files and text files typically compress well, since |
| most such files contain a lot of repeated data. Files that were compressed |
| by using a standalone compression program such as PKZIP usually do not |
| compress any further; although you can store such files on a compressed |
| drive, there is little advantage to doing so. |
|
| Will DoubleSpace slow down my system? |
|
| If you have a computer with a fast CPU and a fast hard disk, you probably |
| won't notice much difference in system speed after installing DoubleSpace. |
| If you have a fast CPU and a slow hard disk, DoubleSpace might actually |
| improve your system's speed. If your computer has a slow CPU, you may notice |
| a reduction in speed after compressing your drive. |
|
| What happens during DoubleSpace Setup? |
|
| DoubleSpace Setup configures your computer to run DoubleSpace and compresses |
| the drive of your choice. DoubleSpace Setup first runs ScanDisk to check |
| your hard disk for logical and physical errors. If necessary, it runs the |
| Microsoft Defragmenter to defragment the files on your disk. Finally, it |
| compresses the files on your drive. For more information about running |
| DoubleSpace Setup, see the "Freeing Disk Space" chapter of the MS-DOS 6 |
| User's Guide. |
|
| Now that I've installed DoubleSpace, why do I have an additional drive? |
|
| When DoubleSpace Setup is complete, you will have an additional drive. |
|
| If you chose to create a new compressed drive, the additional drive is the |
| compressed drive you just created. |
|
| If you compressed an existing drive (for example, drive C) the additional |
| drive is an uncompressed drive. It is used to store files that must remain |
| uncompressed (such as the Windows swap file). The additional drive also |
| contains important system files such as IO.SYS, MSDOS.SYS, DBLSPACE.BIN, |
| DBLSPACE.INI and DBLSPACE.000. |
|
| CAUTION: Do not delete or otherwise tamper with the hidden files on the new |
| drive. If you do, you might lose your compressed drive and all the |
| files it contains. |
|
| For more information about DoubleSpace Setup, see "Understanding Disk |
| Compression" in the "Freeing Disk Space" chapter of the MS-DOS 6 User's |
| Guide. |
|
| Can I copy a file from a compressed drive to an uncompressed drive (such as |
| a floppy disk or a network drive)? |
|
| Yes. You can copy files between compressed drives and uncompressed drives |
| just as you would between two uncompressed drives. A file is actually |
| compressed only when it is stored on a compressed drive. When you copy a |
| file from your compressed drive, DoubleSpace reads the file into memory and |
| uncompresses it. The file is then copied to the uncompressed drive in its |
| uncompressed state. |
|
| If I compress a drive and then add more files to it, do I need to recompress |
| the drive? |
|
| No. Whenever you copy a file to a DoubleSpace drive, DoubleSpace saves the |
| file in compressed form. It doesn't matter whether the file was on the drive |
| when you compressed the drive. |
|
| If I'm using DoubleSpace, what should I do to maintain my system? |
|
| In general, maintaining a computer that's running DoubleSpace is just like |
| maintaining an uncompressed system. To ensure the safety of your data and |
| the stability of your system, do the following frequently (for example, once |
| a week): |
|
| Back up your data files regularly. You can back up your files by using |
| either Backup for MS-DOS or Backup for Windows. For more information, see |
| the following section. Also, see the chapter "Managing Your System" in |
| the MS-DOS 6 User's Guide. |
|
| Check your hard disk regularly for logical and physical errors. To check |
| and repair a drive, use the ScanDisk program. For more information, see |
| SCANDISK . |
|
| Check your computer's memory and hard disk for viruses. Viruses can |
| damage data, and can even prevent your computer from starting or running |
| properly. To check for viruses, use Anti-Virus. Be sure to check all your |
| drives -- compressed and uncompressed drives. For more information, see |
| the chapter "Managing Your System" in the MS-DOS 6 User's Guide. |
|
| Defragment your hard disk drive periodically. (Since defragmentation can |
| take a long time, you might want to do it at the end of the day.) For |
| more information, see the chapter "Managing Your System" in the MS-DOS 6 |
| User's Guide. |
|
| Set up Undelete so that you can restore any files that you accidentally |
| delete. For information about setting up Undelete, see the chapter |
| "Managing Your System" in the MS-DOS 6 User's Guide. |
|
| How should I back up my files if I'm using DoubleSpace? |
|
| You should back up and restore the files on a compressed drive just as you |
| would the files on an uncompressed drive. (For information about using |
| Microsoft Backup, see the chapter "Managing Your System" in the MS-DOS 6 |
| User's Guide.) |
|
| When backing up the files on the host drive (the uncompressed drive that |
| contains the compressed volume file (CVF) for your compressed drive), you |
| typically do not need to back up any files that have names in the form |
| DBLSPACE.nnn (for example, DBLSPACE.000). The DBLSPACE.nnn file essentially |
| contains your compressed drive. Although it is possible to back up the |
| DBLSPACE.nnn file, doing so is redundant if you have also backed up the |
| files on that compressed drive. In general, it's best to back up the files |
| on your compressed drive directly, rather than by backing up the associated |
| CVF (the DBLSPACE.nnn file). This is because backing up only the CVF does |
| not allow you to restore individual files or directories later. When you |
| restore the backup copy of a DBLSPACE.nnn file, it replaces the entire |
| compressed drive with the backup copy. This means that you will lose all |
| changes to all files on that drive that were made since the backup copy was |
| created. |
|
| I installed DoubleSpace and now I'm running out of memory. What can I do? |
|
| If you have an 80386 or higher computer, run MemMaker after installing |
| DoubleSpace. MemMaker can move portions of DoubleSpace out of conventional |
| memory, which makes more memory available for running programs. Also, make |
| sure the BUFFERS command in your CONFIG.SYS file is set to no more than 10 |
| buffers. For more information about BUFFERS and DoubleSpace, see BUFFERS . |
|
| If you have an 80286 computer with at least 1 MB of memory, make sure your |
| CONFIG.SYS file contains a DOS=HIGH command and a DEVICE command for |
| HIMEM.SYS. (MS-DOS Setup normally adds these commands to your CONFIG.SYS |
| file.) With these commands, MS-DOS, and parts of DoubleSpace, can load into |
| the high memory area. |
|
| Is it all right to run SMARTDrive if I'm using DoubleSpace? |
|
| SMARTDrive and DoubleSpace are designed to work together. If Setup |
| determines that your computer has enough memory to run SMARTDrive, it |
| automatically installs SMARTDrive by adding a SMARTDRV command to your |
| AUTOEXEC.BAT file. In particular, you should run SMARTDrive if you are |
| running DoubleSpace and you use Windows; in that case, using SMARTDrive can |
| significantly speed up your computer. |
|
| SMARTDrive is designed to speed up your system and safeguard your data. By |
| default, Setup configures SMARTDrive so that write-caching is disabled. (If |
| SMARTDrive was originally configured to allow write-caching, Setup will not |
| change your configuration.) Write-caching provides much faster performance |
| than read-only caching, but is not as conservative. For more information |
| about SMARTDrive, see SMARTDRV . |
|
