Glossary |
This file lists which clusters are in use. Each bit in this file represents one LCN.
Type | Description | Name |
---|---|---|
0x10 | $STANDARD_INFORMATION | |
0x30 | $FILE_NAME | $Bitmap |
0x80 | $DATA | [Unnamed] |
The lowest bit represents the lowest numbered LCN. Thus:
Bit | LCN |
---|---|
000000012 | 0 |
000000102 | 1 |
000001002 | 2 |
... | etc |
To prevent the MFT becoming fragmented, Windows maintains a buffer around it. No new files will be created in this buffer region until the other disk space is used up. The buffer size is configurable and can be 12.5%, 25%, 37.5% or 50% of the disk. Each time the rest of the disk becomes full, the buffer size is halved.
The size of this file is always a multiple of 8 bytes (64 clusters). Because of this rounding-up, the $Bitmap will represent slightly more clusters than the disk has. These bit are always set to 1.
The backup copy of the boot sector lies in this no-mans-land the cluster is hence marked as in use.
In theory, on very small volume, this attribute could be resident. In practice, Windows crashes.