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| Troubleshooting Hard Disk Drives | Missing
Space Issues ]
There is hard disk space missing on my disk drive; there should be more space free than
there actually is, or the system says the hard disk is full even though there should be
Explanation: You are noticing that while your hard disk is supposed to be able to
hold a certain amount of data, say 2 GB, that it becomes full despite having several
hundred megabytes of less data stored on it. You may also notice for example that you have
a volume with 100 MB of free space but you are unable to copy 90 MB of files to it before
the disk becomes full.
Diagnosis: It is very common to encounter this, especially on larger disks. In most
cases there is really nothing wrong, except that a substantial portion of the storage area
of the disk is wasted. In addition, various software packages can consume large amounts of
hidden storage. File system corruption can legitimately lead to lost storage space.
Recommendation: "Missing" free space on a hard disk is often caused by a
combination of different causes. Try all of the following, since you may find that more
than one applies:
- The most likely cause of this observation is simply that you have probably lost a good
deal of your disk space to what is called slack. Since the FAT file system
allocates space in chunks called clusters, each file can only use a whole number of
clusters. This means that if you create a 1,000-byte file in a volume that uses
16,384-byte clusters, 15,384 bytes are wasted. Multiply that by thousands of files and
this is the cause of many people's missing space problems. Slack is discussed in much more detail here.
- Scan the hard disk for file system
corruption. You should check for file system problems regularly as part of your system
care routine. Various problem situations can cause clusters on the hard disk to be marked
as used when no file is using them, and that space is then legitimately
"missing". Fixing the lost clusters will free up this space. Usually only a
small number of clusters are lost at a given time. If you see lost clusters regularly, troubleshoot that problem here.
- Discrepancies in storage totals of 5-10% are often a result of the fact that some
software uses binary megabytes and gigabytes to measure storage, and other software uses
decimal megabytes and gigabytes. See here for a
more complete discussion.
- If you are using a disk drive that is over 2.1 GB in size and you are not using Windows
95 OEM SR2's FAT32 file system, your hard disk must be broken into multiple partitions to
get full use of the disk. Sometimes vendors will do this without telling their customers
about it, so you may know that you bought a 3.2 GB drive but only be able to see 2.1 GB of
it. In this case, look for another drive letter (typically D:, E: etc.) where you should
be able to see the rest of your hard disk.
- Software that is designed to protect against accidental file deletion works by storing
files you delete in a hidden area on the disk, so that if you later regret deleting them,
you can restore them easily. Windows 95's Recycle Bin does this. Norton Utilities and
other programs add more hidden areas where deleted files are stored. If you don't
carefully monitor the settings on these programs, they can chew up a lot of disk space
with files you thought you had deleted. Windows 95 is smart enough to offer to empty the
Recycle Bin when the disk gets full; I am not sure what Norton does. At any rate,
right-clicking on the Recycle Bin should yield an option to let you empty the Bin, which
may free up some space. If you are using Norton's Unerase or Protection, be particularly wary of it using
large amounts of disk space for its protection routines, and cut back on how much of the
disk it is allowed to use.
- If you are trying to copy a large number of files (over 500) to the root directory of a
drive volume you will find that you cannot, despite having a lot of space on the disk.
This is because the root directory is
limited in size. Regular directories are not limited, so try putting the files in a
- If you have created a compressed volume then part of the host drive will be used to
contain the compressed volume file.
For example, if you have a 1 GB C: partition and use 400 MB of it to create a 700 MB
compressed volume called D:, then C: will of course have 400 MB taken to hold the
- Compressed volumes themselves only
estimate the amount of free space on a volume, because they cannot know how much will
fit on the disk until the files are copied there (since different files compress different
- If you try to create more than one primary DOS partition on a hard disk using a utility
like Partition Magic, or if you have a non-DOS partition on the disk such as a UNIX
partition, that space will be hidden from view when you are running DOS or Windows.
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