Disk Space Needed to Save UNFORMAT Information (71585)
This article was previously published under Q71585
The following error message is displayed when the FORMAT command
cannot find enough free space on the disk to save the UNFORMAT
Drive <x> error. Insufficient space for the MIRROR image file.
There was an error creating the format recovery file.
This disk cannot be unformatted.
Note: <x> refers to either drive A or B or any other external drive.
When the FORMAT command is used without the "/U" option, it tries to
save the UNFORMAT information when reformatting a disk to the same
density. The following is the minimum space required in the last 25
percent of the disk space for the FORMAT command to create a MIRROR
Disk Size Capacity Free Space Needed
--------- -------- -----------------
5.25 inches 360K 7,168 bytes
5.25 inches 1.2 MB 12,800 bytes
3.5 inches 720K 8,192 bytes
3.5 inches 1.44 MB 13,824 bytes
The FORMAT command in MS-DOS version 5.0 examines the disk to
determine if it has already been formatted. If the disk has been
formatted, the FORMAT command attempts to create a MIRROR image file
before reformatting the disk. When FORMAT finds that there is not
enough room on the disk to create a MIRROR image file, it displays the
error message and gives you an option to continue with FORMAT. If you
choose to continue, the MIRROR image file is not created, and the
UNFORMAT command will not be able to recover the old information from
the newly formatted disk.
A MIRROR image file contains the information that the UNFORMAT command
needs to unformat the disk. MIRROR image files can also be created
with the MIRROR command. For more information on MIRROR, FORMAT, and
UNFORMAT, query on the following words:
The UNFORMAT information consists of Boot Sector, File Allocation
Table, and Root Directory, which is stored in the MIRROR image file.
The requirement of free space in the last 25 percent of the disk space
is imposed to prevent UNFORMAT from taking an extensive amount of time
when trying to find the control file anywhere on the disk.
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